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As filed with the Securities and Exchange Commission on June 27, 2003
Registration No. 333-            

SECURITIES AND EXCHANGE COMMISSION
 Washington, D.C. 20549

Form S-8
 Registration Statement
Under
The Securities Act of 1933

Aon Corporation
 (Exact name of Registrant as Specified in Its Charter)

Delaware 
(State or Other Jurisdiction
of Incorporation or Organization)	
 	
36-3051915 
(I.R.S. Employer
Identification Number)	

Aon Center
200 East Randolph Drive
Chicago, Illinois 
(Address of Principal Executive Offices)	
 	
60602 
(Zip Code)	
Aon Deferred Compensation Plan
 (Full Title of the Plan)
Raymond I. Skilling
 Executive Vice President and Chief Counsel
Aon Corporation
Aon Center
200 East Randolph Drive
Chicago, Illinois 60602
(312) 701-3000
(Name, Address and Telephone Number, Including Area Code, of Agent for Service)
 
Calculation of Registration Fee

Title of Each Class of
Securities to be Registered	 	Amount to be
Registered	 	Proposed Maximum
Offering Price
Per Unit	 	Proposed Maximum
Aggregate Offering
Price	 	Amount of
Registration Fee	
	
Aon Deferred
Compensation Obligations	 	$50,000,000	 	N/A(1)	 	$50,000,000(1)	 	$4045	
	
(1)
The Aon Stock Deferred Compensation Obligations are unsecured obligations of Aon Corporation to make distributions in the future in accordance with the terms of the Aon Deferred Compensation Plan.

 
 Part II
Information Required in the
Registration Statement
  Item 3.     Incorporation of Certain Documents by Reference
        The following documents heretofore filed (File Number 1-7933) with the Securities and Exchange Commission (the "Commission") by Aon Corporation (the "Company") are incorporated herein by reference:
(a)
Annual Report on Form 10-K for the year ended December 31, 2002;

(b)
Quarterly Report on Form 10-Q for the quarter ended March 31, 2003; and

(c)
Current Reports on Form 8-K filed with the Commission on January 9, February 20, May 2 and May 5, 2003.
        All documents filed by the Company pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), after the date of this Registration Statement and prior to the filing of a post-effective amendment which indicates that all securities offered hereby have been sold or which deregisters all securities then remaining unsold, are deemed to be incorporated by reference into this Registration Statement and to be a part hereof from the respective dates of filing of such documents (such documents, and the documents enumerated above, being hereinafter referred to as "Incorporated Documents").
        Any statement contained in an Incorporated Document shall be deemed to be modified or superseded for purposes of this Registration Statement to the extent that a statement contained herein or in any other subsequently filed Incorporated Document modifies or supersedes such statement. Any such statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this Registration Statement.
 
 Item 4.     Description of Securities
         Aon Deferred Compensation Obligations .    The $50,000,000 of deferred compensation obligations (the "Obligations") being registered hereby may be offered to eligible employees of the Company and its subsidiaries pursuant to the Aon Deferred Compensation Plan (the "Plan"). In a given year, this group of eligible employees (each, a "Participant") includes certain members of management and other highly compensated employees of the Company and its subsidiaries.
        For each calendar year, the Plan provides each Participant with the opportunity to elect to defer up to 75% of the Participant's bi-weekly compensation and up to 100% of the Participant's bonus, if any, earned in that year. The amount of total compensation deferred by each Participant is determined in accordance with that Participant's deferral election and the provisions of the Plan. The Plan provides for the tracking of each Participant's deferred amounts in valuation funds elected by that Participant from among various investment options. The Company maintains separate bookkeeping accounts for each Participant. The amounts in each Participant's accounts represent an obligation of the Company to pay the Participant at some time in the future.
        The amounts payable to Participants under the Plan are distributed in accordance with the distribution provisions of the Plan. Generally, a Participant may elect to receive distributions prior to or subsequent to termination of the Participant's employment, in either (i) up to five annual installments, in the case of distributions to be received prior to termination, or up to ten annual installments, in the case of distributions to be received subsequent to termination, or (ii) a lump-sum. Participants may be entitled to an early distribution in the event of certain immediate financial needs and also may request an early distribution of a portion of their deferred amount upon payment of a significant penalty. Upon the death of a Participant, the Participant's designated beneficiary or estate will receive the undistributed amounts in accordance with the provisions of the Plan. Distributions pursuant to the Plan will be made in cash.
        The Obligations are general unsecured obligations of the Company to pay, in the future, compensation deferred in accordance with the terms of the Plan, and with the procedures established by the Committee, from the general assets of the Company. These Obligations rank pari passu with other unsecured and unsubordinated indebtedness of the Company from time to time outstanding.
        The Obligations cannot be assigned, transferred, pledged or encumbered, or be subject in any manner to alienation or anticipation.
II-1

        The Board of Directors of the Company may amend, modify or terminate the Plan at any time, provided that such amendment, modification or termination does not adversely affect the rights of a Participant with respect to amounts accrued in the Participant's bookkeeping accounts unless that Participant has consented to the amendment, modification or termination.
 
 Item 5.     Interests of Named Experts and Counsel
        Not applicable.
 
 Item 6.     Indemnification of Directors and Officers
        The Company was organized under the laws of the State of Delaware and is subject to the Delaware General Corporation law. Delaware law provides that officers and directors may receive indemnification from their corporations for certain actual or threatened lawsuits. Delaware law sets out the standard of conduct that the officers and directors must meet in order to be indemnified, the parties who are to determine whether the standard has been met and the types of expenditures which will be indemnified. Delaware law further provides that a corporation may purchase indemnification insurance, such insurance providing indemnification for the officers and directors whether or not the corporation would have the power to indemnify them against such liability under the provisions of Delaware law.
        The Company's Second Restated Certificate of Incorporation, as amended, provides that it will indemnify its officers and directors to the fullest extent permitted by Delaware law.
        In addition, the Company maintains insurance coverage that provides reimbursement within the policy limits for amounts it is obligated to pay arising out of lawsuits involving officers and directors serving in such capacities in which the damages, judgments, settlements, costs, charges or expenses incurred in connection with the defense of the action, suit or proceeding are reimbursable pursuant to Delaware law and the Company's Second Restated Certificate of Incorporation, as amended.
 
 Item 7.     Exemption from Registration Claimed
        Not applicable.
II-2

 
 Item 8.     Exhibits

Exhibit
Number
	 	Description of Exhibit
	
4.1	 	Second Restated Certificate of Incorporation of the Company incorporated by reference to Exhibit 3(a) to the Company's Annual Report on Form 10-K for the year ended December 31, 1991.	

4.2	
 	
Certificate of Designation for the Company's Series C Cumulative Preferred Stock incorporated by reference to Exhibit 4.1 to the Company's Current Report on Form 8-K dated February 9, 1994.	

4.3	
 	
Certificate of Amendment of the Company's Second Restated Certificate of Incorporation incorporated by reference to Exhibit 3 to the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 1994.	

4.4	
 	
Certificate of Amendment of the Company's Second Restated Certificate of Incorporation incorporated by reference to Exhibit 3 to the Company's Current Report on Form 8-K filed on May 9, 2000.	

4.5	
 	
Amended Bylaws of the Company incorporated by reference to Exhibit 3.2 to the Company's Current Report on Form 8-K filed on October 4, 2002.	

*4.6	
 	
Aon Deferred Compensation Plan.	

*5	
 	
Opinion of Richard E. Barry, Senior Counsel and Assistant Secretary of the Company as to the legality of the securities being registered.	

*15	
 	
Acknowledgement of Ernst & Young LLP.	

*23.1	
 	
Consent of Richard E. Barry (included in the opinion filed as Exhibit 5).	

*23.2	
 	
Consent of Ernst & Young LLP.	

*24	
 	
Powers of Attorney.	

*
Filed herewith.
 
 Item 9.     Undertakings
        (a)   The undersigned Registrant hereby undertakes:
        (1)   To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:
          (i)  To include any prospectus required by Section 10(a)(3) of the Securities Act of 1933, as amended (the "Securities Act");
         (ii)  To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement; and notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Commission pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20 percent change in the maximum aggregate offering price set forth in the "Calculation of Registration Fee" table in the effective registration statement; and
        (iii)  To include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement;
provided , however , that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply if the registration statement is on Form S-3, Form S-8 or Form F-3, and the information required to be included in a post-effective amendment by those paragraphs is contained in periodic reports filed with or furnished to the Commission by the Registrant pursuant to Section 13 or 15(d) of the Exchange Act that are incorporated by reference in the registration statement.
II-3

        (2)   That, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.
        (3)   To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.
        (b)   The undersigned Registrant hereby undertakes that, for purposes of determining any liability under the Securities Act, each filing of the Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the Exchange Act (and, where applicable, each filing of an employee benefit plan's annual report pursuant to Section 15(d) of the Exchange Act) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.
        (c)   Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the Registrant pursuant to the foregoing provisions, or otherwise, the Registrant has been advised that in the opinion of the Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer or controlling person of the Registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.
II-4

 Signatures
        Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Chicago, State of Illinois, on this 27th day of June, 2003.

 	
Aon Corporation	

By:	
/s/ Patrick G. Ryan

Patrick G. Ryan
Chairman and Chief Executive Officer	

Signature

Title(s)

Date Signed

 	

 	
 	
/s/   PATRICK G. RYAN       

Patrick G. Ryan	 	Chairman, Chief Executive Officer, and Director (Principal Executive Officer)	 	June 27, 2003	

/s/   DAVID P. BOLGER       

David P. Bolger	
 	
Executive Vice President and Chief Financial Officer (Principal Financial and Accounting Officer)	
 	
June 27, 2003	

*

Edgar D. Jannotta	
 	
Director	
 	
June 27, 2003	

*

P.J. Kalff	
 	
Director	
 	
June 27, 2003	

*

Lester B. Knight	
 	
Director	
 	
June 27, 2003	

*

J. Michael Losh	
 	
Director	
 	
June 27, 2003	

*

R. Eden Martin	
 	
Director	
 	
June 27, 2003	

*

Andrew J. McKenna	
 	
Director	
 	
June 27, 2003	

*

Robert S. Morrison	
 	
Director	
 	
June 27, 2003	

II-5

*

Richard C. Notebaert	
 	
Director	
 	
June 27, 2003	

*

Michael D. O'Halleran	
 	
President, Chief Operating Officer and Director	
 	
June 27, 2003	

*

John W. Rogers, Jr.	
 	
Director	
 	
June 27, 2003	

*

George A. Schaefer	
 	
Director	
 	
June 27, 2003	

*

Carolyn Y. Woo	
 	
Director	
 	
June 27, 2003	

*By:	
 	
/s/   PATRICK G. RYAN       

Patrick G. Ryan
 Attorney-in-Fact	

 	
 	
II-6

 Index to Exhibits to Registration Statement on Form S-8

Exhibit
Number
	 	Description of Exhibit
	
4.1	 	Second Restated Certificate of Incorporation of the Company incorporated by reference to Exhibit 3(a) to the Company's Annual Report on Form 10-K for the year ended December 31, 1991.	

4.2	
 	
Certificate of Designation for the Company's Series C Cumulative Preferred Stock incorporated by reference to Exhibit 4.1 to the Company's Current Report on Form 8-K dated February 9, 1994.	

4.3	
 	
Certificate of Amendment of the Company's Second Restated Certificate of Incorporation incorporated by reference to Exhibit 3 to the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 1994.	

4.4	
 	
Certificate of Amendment of the Company's Second Restated Certificate of Incorporation incorporated by reference to Exhibit 3 to the Company's Current Report on Form 8-K filed on May 9, 2000.	

4.5	
 	
Amended Bylaws of the Company incorporated by reference to Exhibit 3.2 to the Company's Current Report on Form 8-K filed on October 4, 2002.	

*4.6	
 	
Aon Deferred Compensation Plan.	

*5	
 	
Opinion of Richard E. Barry, Senior Counsel and Assistant Secretary of the Company as to the legality of the securities being registered.	

*15	
 	
Acknowledgement of Ernst & Young LLP.	

*23.1	
 	
Consent of Richard E. Barry (included in the opinion filed as Exhibit 5).	

*23.2	
 	
Consent of Ernst & Young LLP.	

*24	
 	
Powers of Attorney.	

*
Filed herewith.
II-7

QuickLinks
 Part II Information Required in the Registration Statement
Item 3. Incorporation of Certain Documents by Reference
Item 4. Description of Securities
Item 5. Interests of Named Experts and Counsel
Item 6. Indemnification of Directors and Officers
Item 7. Exemption from Registration Claimed
Item 8. Exhibits
Item 9. Undertakings
 Signatures
 Index to Exhibits to Registration Statement on Form S-8
 
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 Exhibit 4.6
 
 AON DEFERRED COMPENSATION PLAN
(As Amended and Restated Effective as of November 1, 2002)

 TABLE OF CONTENTS

 	 	Page
	
PREAMBLE	 	1	

SECTION 1	
 	
1	
 	Definitions	 	1	

SECTION 2	
 	
3	
 	Eligibility	 	3	
 	 	2.01    Eligibility	 	3	
SECTION 3	 	4	
 	Election To Defer	 	4	
 	 	3.01    Irrevocable Election	 	4	
 	 	3.02    First Calendar Year Election	 	4	

SECTION 4	
 	
5	
 	Deferred Compensation Amounts and Investment Elections	 	5	
 	 	4.01    Deferral Period Accounts	 	5	
 	 	4.02    Investment Elections	 	5	
 	 	4.03    Amounts Credited to the Aon Common Stock Account	 	5	
 	 	4.04    Earnings Credited to the Aon General Account	 	5	
 	 	4.05    Amounts Credited to Other Investment Accounts	 	6	

SECTION 5	
 	
7	
 	Method of Distribution	 	7	
 	 	5.01    Method of Distribution	 	7	
 	 	5.02    Installment Payments	 	7	
 	 	5.03    Withdrawals for Immediate Financial Need	 	7	
 	 	5.04    Withdrawals with Significant Penalty	 	8	
 	 	5.05    Distribution Upon Death	 	8	
 	 	5.06    Distribution of Small Amounts	 	8	
 	 	5.07    Form of Distribution	 	8	

SECTION 6	
 	
9	
 	Miscellaneous	 	9	
 	 	6.01    Participant's Rights and Interest in the Accounts	 	9	
 	 	6.02    Nonalienability and Nontransferability	 	9	
 	 	6.03    Plan Administrator	 	9	
 	 	6.04    Amendment and Termination	 	9	

SECTION 7	
 	
10	
 	General Provisions	 	10	
 	 	7.01    Controlling Law	 	10	
 	 	7.02    Facility of Payment	 	10	
 	 	7.03    Withholding of Payroll Taxes	 	10	
 	 	7.04    Liability	 	10	
 	 	7.05    Successors	 	10	
SUPPLEMENT A	 	 	
SUPPLEMENT B	 	 	
i

AON DEFERRED COMPENSATION PLAN
Preamble
        Aon Corporation ("Aon" or "Company") has previously adopted two nonqualified deferred compensation plans for the benefit of certain select management or highly compensated employees of Aon or its subsidiaries. One such plan was effective as of October 1, 1994 and provided for deferrals for years 1994 through 1998 (including deferrals of bonuses earned in 1998 payable in 1999) (the "1994 Plan"). The other plan was effective as of January 1, 1999 and provided for deferrals for years 1999 through 2002 (including regular compensation and bonuses paid for services performed through October 31, 2002 and deferrals of bonuses earned in 2001 payable in 2002) (the "1999 Plan").
        Effective as of November 1, 2002, the 1994 Plan and 1999 Plan are hereby merged, and amended and restated, provided, however, that the provisions set forth in Supplements A and B, respectively, will continue to apply to the deferrals made under the 1994 Plan and 1999 Plan, to the extent the provisions in those Supplements are inconsistent with the provisions set forth herein.
        The purpose of this plan is also to provide certain select management or highly compensated employees of Aon and its subsidiaries with the opportunity to defer amounts earned as an employee between November 1, 2002 and December 31, 2002, and calendar years thereafter. The Plan shall generally be effective as of November 1, 2002, and will be known as the Aon Deferred Compensation Plan (As Amended and Restated as of November 1, 2002) (the "Plan").
 
 SECTION 1

Definitions
        1.01 "Accounts" shall mean the Distribution Accounts and Investment Accounts.
        1.02 "Administrative Committee" shall mean the Administrative Committee under the Aon Savings Plan.
        1.03 "Aon Common Stock Account" shall mean the account established on the books of the Company or a Subsidiary for a Participant who has elected to allocate any deferral into Aon Common Stock. The Aon Common Stock Account shall be considered an Investment Account hereunder, and shall be available for deferrals under the 1994 Plan and 1999 Plan and may be available for deferrals thereafter, in the discretion of the Company.
        1.04 "Aon General Account" shall mean the account established on the books of the Company or a Subsidiary for a Participant who has elected to allocate any deferral into the Aon General Account. The Aon General Account shall be considered an Investment Account hereunder and shall be available for deferrals under the 1994 Plan and 1999 Plan and may be available for deferrals thereafter, in the discretion of the Company.
        1.05 "Beneficiary" shall mean the beneficiary or beneficiaries designated by the Participant to receive the amount, if any, payable under the Plan upon the death of the Participant.
        1.06 "Board" shall mean the board of directors of the Company.
        1.07 "Company" shall mean Aon Corporation.
        1.08 "Compensation" shall mean the following types of earnings paid to an Employee for his service on behalf of the Company or the Subsidiaries; salary and fixed base compensation including compensation for overtime, and net commission, renewal and override compensation. Compensation shall also mean amounts paid by the Company pursuant to but not limited to a periodic individual performance appraisal or contractual agreement ("Bonus"). The following shall not be included in Compensation: (i) deferred compensation payments; (ii) stock awards; (iii) income from the exercise of stock options; (iv) expense reimbursements; (v) distributions from, and Company or Subsidiary contributions to, the Aon Savings Plan, the Aon Employee Stock Ownership Plan, the Aon Pension Plan or any other Company or Subsidiary fund or plan providing retirement, health, welfare, death, insurance or similar benefits; (vi) amounts paid to an Employee in respect to employment during which he is not permanently employed within the United States or its possessions; and (vii) amounts previously deferred under the terms of the Plan.
        1.09 "Distribution Accounts" shall mean, for deferrals on Compensation paid on and after November 1, 2002, the Accounts established by the Administrative Committee to reflect the distribution method selected by a Participant. If the Employee elects to begin distributions before termination of employment, the Distribution Account shall be known as an "In-Service Account." If a Participant elects to begin distributions in the year following termination of employment, the Distribution Account shall be known as a "Retirement Account." A Participant may select one or two distribution methods to begin before termination of employment, and therefore

the Administrative Committee may establish one or two "In-Service Accounts" for a Participant. The Participant may select only one distribution method to begin after termination of employment, and therefore the Administrative Committee may establish only one Retirement Account for a Participant. For deferrals on Compensation under the 1994 Plan or 1999 Plan which have not begun by November 1, 2002, the Administrative Committee will change the distribution method to correspond to the distribution method which most closely corresponds to the method selected for deferrals on Compensation paid after November 1, 2002. For deferrals on Compensation under the 1994 Plan or 1999 Plan which have begun by November 1, 2002, the Administrative Committee will create a Distribution Account for each distribution method in effect.
        1.10 "Employee" shall mean any United States staff employee of the Company or any Subsidiary.
        1.11 "Investment Accounts" shall mean, for deferrals on Compensation paid on or after November 1, 2002, the Accounts established by the Administrative Committee to reflect the investment alternatives selected by the Participant from among the investment alternatives made available by the Company under Section 4.02 of the Plan. These Investment Accounts will be established under each Distribution Account to reflect the investment alternative(s) elected by the Participant for that Distribution Account.
        1.12 "Participant" shall mean any eligible Employee who elects to participate in the Plan pursuant to Section 2.
        1.13 "Plan" shall mean the Aon Deferred Compensation Plan (As Amended and Restated Effective as of November 1, 2002).
        1.14 "Subsidiary" shall mean any corporation of which 50% or more of the voting stock is owned or controlled, directly or indirectly, by the Company or by one or more of such corporations.
2

 
 SECTION 2

Eligibility
2.01 Eligibility
        Any Employee of the Company or a Subsidiary who received wages or compensation as reported on Box 5 of IRS Form W-2 of $150,000 or more in the prior calendar year or whose rate of annual base pay in the current calendar year is $150,000 or more shall be eligible to participate in the Plan, unless otherwise decided by the Board or the Administrative Committee. In addition, other select management or highly compensated Employees may be eligible to participate at the option of the Administrative Committee. Every eligible Employee shall become a Participant after making an irrevocable election to participate as described in Sections 3.01 or 3.02.
3

 
 SECTION 3

Election To Defer
3.01 Irrevocable Election
        On or before November 1, 2002, each Employee eligible to participate in the Plan should be entitled to make an irrevocable election to defer receipt of any whole percentage (up to 75%) of bi-weekly Compensation paid to the Employee for his services as an Employee for the Company or a Subsidiary for the period from November 1, 2002 through December 31, 2002. Prior elections executed in 2001 for bonuses earned in 2002 shall not be changed. Thereafter, on or before December 31 of any year, each Employee eligible to participate in the Plan shall be entitled to make an irrevocable election to defer receipt of: (i) any whole percentage (up to 75%) of bi-weekly Compensation paid to the Employee for his services as an Employee from the Company or a Subsidiary for the following calendar year: and (ii) any whole percentage (up to 100%) of any Bonus to be earned for services performed in the following calendar year.
        Each Participant will need to make an affirmative election to make deferrals hereunder for each calendar year, in accordance with rules established by the Administrative Committee.
3.02 First Calendar Year Election
        Within 30 days after an Employee is notified of his eligibility to participate in the Plan, but no later than 60 days after an Employee first becomes eligible to participate in the Plan, he or she shall be entitled to make an irrevocable election to defer any whole percentage of Compensation not yet payable for the remainder of that calendar year.
4

 
 SECTION 4

Deferred Compensation Amounts and Investment Elections
4.01 Deferral Period Accounts
        The Administrative Committee shall establish Distribution Accounts and Investment Accounts for any Employee who made a deferral under the 1994 Plan or 1999 Plan or who makes a deferral on Compensation paid on or after November 1, 2002. The Administrative Committee shall establish such other subaccounts as are necessary for proper administration under the Plan.
4.02 Investment Elections
        For deferrals on Compensation paid on and after November 1, 2002, the Company will select the investment alternatives available to the Participants, and the Company shall establish an Investment Account for each available investment alternative. The Participant may make a separate investment election for each Distribution Account created under Section 5.01, except that such investment election shall not apply to any deferrals made under the 1994 Plan or 1999 Plan.
        Each Participant making an election to defer amounts shall also elect how the deferred amount will be allocated to the Investment Accounts. For deferrals under the 1994 Plan or 1999 Plan, if a Participant has elected to allocate any deferrals to the Aon General Account, the Participant may, in accordance with rules established by the Administrative Committee, change such allocation to the Aon Common Stock Account. However, for deferrals under the 1999 Plan, a Participant may not change any allocation from the Aon Common Stock Account to the Aon General Account.
        If a Participant fails to make an investment allocation, any deferral shall be allocated to the Investment Account representing a money market fund. With respect to deferrals made on Compensation paid on or after November 1, 2002, Participants may make reallocations of such amounts among the existing investment alternatives on any business day, except that the Administrative Committee may impose whatever restrictions it deems advisable, including restrictions which may apply only to certain Participants in the Plan and restrictions designed to prevent violation of the federal securities laws.
4.03 Amounts Credited to the Aon Common Stock Account
        For any deferral allocated to the Aon Common Stock Account after November 1, 2002, the amount of shares so credited will be determined by dividing the deferred amount by the Fair Market Value of Aon common stock on the New York Stock Exchange. Deferrals will be credited to the Employee's account as soon as administratively possible after the day such deferral would have been payable to the Participant had it not been deferred. The "Fair Market Value" of Aon common stock on any day is the closing price, regular way, as reported by an independent pricing service selected by the Administrative Committee.
        As of the date any cash dividends are paid on Aon common stock, each Participant's Aon Common Stock Account shall be credited with the dividends that would be paid with respect to Aon common stock on that date as if the Participant owned the stock credited under the Aon Common Stock Account. Dividends will be treated as if they are reinvested in whole or fractional shares of Aon common stock on the dividend date, based on the Fair Market Value on that date.
4.04 Earnings Credited to the Aon General Account
        Earnings credited to the Aon General Account shall be determined as follows: the credited rate will be the six-month Treasury bill yield rate, determined as of each January 1 and July 1 by averaging this yield as published monthly by the Federal Reserve Bank of St. Louis on a bank discount basis through the secondary market for the last six months immediately prior to the applicable January 1 or July 1. After this yield is determined as of each January 1 and July 1, the yield will remain effective for the entire 6-month period. The rate of interest may be modified prospectively (applying to all deferrals) by the Board at any time in its exclusive discretion.
5

4.05 Amounts Credited to Other Investment Accounts
        If any deferral is allocated to an Investment Account other than the Aon Common Stock Account or Aon General Account, such deferral shall be credited as soon as administratively feasible after the day such amount would have been payable to the Participant had it not been deferred. The amount of shares so credited to the Account will be determined by dividing the deferred amount by the Fair Market Value of the investment alternative. The "Fair Market Value" of that alternative is the last sales/purchase price of that alternative on that day. If dividends are paid on the Investment Account, the dividends will be treated as reinvested in that investment alternative, based on its Fair Market Value on that date.
        If a Participant changes his or her investment alternative, any amount invested or disinvested in any alternative investment will be done as soon as administratively feasible at the Fair Market Value of that alternative investment on that day.
6

 
 SECTION 5

Method of Distribution
5.01 Method of Distribution
        A Participant may elect up to three different distribution forms of payments and these forms may differ as to the timing of commencement of payments or distribution period, or both. These elections will apply to all deferrals on or after November 1, 2002. A Participant may elect up to two different forms of payment which will apply to payments before termination of employment (the "In-Service Accounts") and one form of payment which will apply to payment after termination of employment (the "Retirement Account"). For Participants who elected distribution forms for deferrals under the 1994 Plan or 1999 Plan and who have not received any payments before November 1, 2002, the Administrative Committee will modify the distribution form selected by the Participant to the one which most closely corresponds to a distribution form of payment selected by the Participant for deferrals made after November 1, 2002.
        When the Participant elects to defer any Compensation or any Bonus pursuant to Section 3, the Participant shall also make an irrevocable election as to the beginning year of distribution with respect to amounts so credited to the Distribution Accounts of the Participant. Pursuant to rules established by the Administrative Committee, such elections may provide for distributions to commence before a Participant's termination of employment (the "In-Service Accounts") or by the February 28 of the year after the Participant's termination of employment with Aon and its Subsidiaries (the "Retirement Account").
        If a Participant elects to commence distributions before termination of employment with Aon and its Subsidiaries, an In-Service Account will be established and the Participant may elect payment in annual installments not in excess of five or in a lump sum, but the commencement date must be later than 3 years after the Participant's first deferral. If a Participant elects to commence distributions after termination of employment with Aon and its Subsidiaries, a Retirement Account will be established, and the Participant may elect payment in annual installments not in excess of ten or in a lump sum. If a Participant has elected to commence distributions in a particular year before termination of employment, but he or she terminates employment with Aon and its Subsidiaries before such date, distributions to the Participant will be pursuant to the election that the Participant made for amounts distributed from the Retirement Account. If a Participant fails to make an election for amounts to be distributed from the Retirement Account, then distributions from the In-Service Accounts will be paid in three annual installments, beginning as soon as administratively possible after February 28 of the year following termination of employment, based on the balance as of that February 28.
        Payments due before termination of employment for any calendar year will be made as soon as administratively possible after February 28 of such year based on the balance as of that February 28. Payments due on account of termination of employment will be made as soon as administratively feasible after February 28 of the next following year based on the balance as of that February 28.
        Notwithstanding any provision herein to the contrary, the Administrative Committee may in its sole discretion modify any distribution election hereunder, to delay or accelerate any payment.
5.02 Installment Payments
        If the Participant has elected installment payments, the amount of the first payment shall be a fraction of the total balances of the Participant's Distribution Accounts as of the applicable February 28, the numerator of which is one and the denominator of which is the total number of installments elected. The amount of each subsequent payment shall be a fraction of the total balances of the Participant's Distribution Accounts similarly computed for each subsequent payment, the numerator of which is one and the denominator of which is the total number of installments remaining. Each installment shall be withdrawn proportionately from the Aon Common Stock Account and Aon General Account and whatever other Investment Accounts of the Participants exist.
5.03 Withdrawals for Immediate Financial Need
        Amounts deferred under the Plan may be distributed earlier than due to the Participant or Beneficiary at the discretion of the Administrative Committee based on the immediate financial need of the Participant or the Beneficiary. Such distributions shall occur only if the Participant dies, becomes disabled or suffers an extreme financial hardship occasioned by a tragic event. Extreme financial hardship means an immediate catastrophic
7

financial need occasioned by (1) an event such as death, total disability, serious injury or illness of a spouse, participant or dependent, or (2) extreme financial reversal or other impending catastrophic event which has resulted in or will result in harm to the Participant, his or her spouse, parents or dependents. Adequate proof of extreme financial hardship must be provided to the Committee. Distributions for extreme financial hardship may not exceed the amount required to meet the hardship and may be made only if the Committee finds that extreme financial hardship may not be met from other resources reasonably available to the participant including liquidation of investment assets, liquidation of luxury assets, loans from financial institutions or other sources. If a hardship distribution is granted, deferrals for the remainder of that calendar year shall cease.
        Withdrawals shall be made in the following order: (1) from the Distribution Account with the closest payment date to the date of withdrawal; (2) to the extent not yet satisfied, from the Distribution Account with the next closest payment date, and so forth. Amounts distributed from each Distribution Account shall be taken pro rata from all Investment Accounts within that specified Distribution Account.
5.04 Withdrawals with Significant Penalty
        Participants may request a distribution of a portion of their Distribution Accounts if they are willing to "forfeit" an amount equal to 10% of the amount distributed. If such a withdrawal is made, all deferrals for the remainder of that calendar year shall cease.
        Withdrawals shall be made in the following order: (1) from the Distribution Account with the closest payment date to the date of withdrawal; (2) to the extent not yet satisfied, from the Distribution Account with the next closest payment date, and so forth. Amounts distributed from each Distribution Account shall be taken pro rata from all Investment Accounts within that specified Distribution Account.
5.05 Distribution Upon Death
        If any Participant dies when installment payments are being paid to the Participant, the unpaid amounts in the Participant's Distribution Accounts shall be paid to the Participant's Beneficiary in accordance with the time period selected by the Participant. If any Participant dies when installment payments are not being paid to the Participant, such unpaid amounts shall be paid to the designated beneficiary beginning in the year after the Participant's death, and shall be paid in accordance with the time period selected by the Participant for payments at termination. If a Beneficiary dies after the Participant but before payments have commenced, payment will be made to the Beneficiary's estate in a single lump sum. If a Participant fails to designate a beneficiary, the amounts payable hereunder shall be made to the Participant's estate in a single lump sum. If a Beneficiary predeceases the Participant, amounts payable hereunder shall be made to the contingent Beneficiary, but if none or if not living, payments shall be made to the Participant's estate in a single lump sum.
5.06 Distribution of Small Amounts
        If at the commencement of benefit payments or after distributions have begun to a Participant or Beneficiary the total balance of a Participant's Distribution Accounts becomes less than $50,000, the Administrative Committee will direct the payment of the remaining amount to the Participant or Beneficiary in a lump sum, notwithstanding any distribution election requiring further installment payments.
5.07 Form of Distribution
        Distributions from the Aon Common Stock Account for deferrals prior to November 1, 2002 must be distributed in the form of shares of Aon Common Stock, except the account balance attributable to deferrals made prior to January 1, 1999 may be paid in cash if elected by the Participant. All other distributions will be in the form of cash.
8

 
 SECTION 6

Miscellaneous
6.01 Participant's Rights and Interest in the Accounts
        No provision in this Plan shall be construed to give any Participant the right to be retained in the Company's or a Subsidiary's service or to any benefits not specifically provided by the Plan. Neither a Participant nor a Beneficiary shall have any interest in the deferred compensation or earnings credited to his accounts other than as an unsecured general creditor of the Company. All amounts deferred or otherwise held for the account of a Participant or a Beneficiary under the Plan shall remain the sole property of the Company or Subsidiary. The Company may or may not decide to purchase an annuity or insurance contract intended to mirror the performance of the investment elections made by the Participants or Beneficiaries, but in all circumstances such annuity or insurance contract will be owned by the Company.
6.02 Nonalienability and Nontransferability
        The rights of a Participant to the payment of deferred compensation as provided in the Plan shall not be assigned, transferred, pledged or encumbered, or be subject in any manner to alienation or anticipation. No Participant may borrow against his Accounts. No Accounts shall be subject in any manner to anticipation, alienation, sale, transfer, assignment, pledge, encumbrance, charge, garnishment, execution, or levy of any kind, whether voluntary or involuntary, including any liability which is for alimony or other payments for the support of a spouse or former spouse, or for any other relative of any Participant.
6.03 Plan Administrator
        The administrator of the Plan shall be the Administrative Committee, which shall have authority to adopt rules and regulations for carrying out the Plan, to delegate its administrative responsibilities as it shall, from time to time, deem advisable, and to interpret, construe, and implement the provisions thereof, in its complete discretion. Any decision or interpretation of any provision of the Plan adopted by the Administrative Committee shall be final and conclusive.
        If a recapitalization, stock dividend (including a spinoff dividend), combination or exchange of shares, merger, consolidation, rights offering, separation, reorganization, liquidation or any other change in the corporate structure of the Company or its shares occurs, the Administrative Committee may make such equitable adjustments to prevent the enlargement or dilution of rights, as it may deem appropriate in the number and class of shares of Aon common stock so credited.
6.04 Amendment and Termination
        The Plan may, at any time, be amended, modified, or terminated by action of the Board. No amendment, modification, or termination shall, without the consent of a Participant, adversely affect such Participant's rights with respect to amounts accrued in his or her Accounts.
9

 
 SUPPLEMENT A
1.
Purpose. The provisions of this Supplement A shall apply to any deferrals made under the 1994 Plan. To the extent these provisions are inconsistent with any other provision of the Plan, the provisions herein shall govern.

2.
Allocations. Any Participant or Beneficiary may elect, within rules established by the Administrative Committee, to allocate amounts from the Aon Common Stock Account to the Aon General Account, and vice versa.

3.
Distributions. If a participant has made an election to have distributions commence before termination of employment, has selected a distribution period exceeding five annual installments and such distributions have not begun by December 31, 2001, such election shall be amended to reduce the installment period to five years, retaining the initial year of commencement. Any distribution which has not commenced by November 1, 2002 will be modified by the Administrative Committee in accordance with Section 5.01 of the Plan. If a Participant who has died does not have a beneficiary designation on file, the amounts payable shall be paid to the person or entity entitled to receive the distribution of the Participant's accounts under the Aon Savings Plan. If such a Participant did not have an account balance under the Aon Savings Plan, the amounts shall be paid to the Participant's estate. If a Beneficiary designated by a Participant fails to survive the Participant by at least ten days, the Participant's beneficiary designation is deemed to be ineffective.

4.
If a Change of Control (as defined below), the Company shall establish an irrevocable grantor trust and shall make the contributions to the trust necessary to make the payments which the Participants and Beneficiaries were entitled under the 1994 Plan on the date of the change of control. Any payments by the trust shall reduce (dollar for dollar) the amounts owed to the Participant or Beneficiary by the Company. This provision is nonamendable by the Company. Change of Control shall mean: (a) the purchase or other acquisition by any person (as defined by Sections 13(d) or 14(d)(2) of the Securities Exchange Act of 1934 (the "Act") or any comparable successor provisions) of beneficial ownership (within the meaning of Rule 13d-3 under the Act) of 20% or more of either the outstanding shares of common stock or the combined voting power of the Company's then outstanding voting securities entitled to vote generally; or (b) the consummation of a merger or equivalent combination in which the Company is not the continuing or surviving corporation, or pursuant to which shares of Aon common stock are converted into cash, securities or other property, other than a merger of the Company in which the holders of Aon common stock immediately prior to the merger have substantially the same proportionate ownership of common stock of the surviving corporation immediately after the merger; or (c) the election by stockholders of members of the Board, 20% or more of whom are persons who were not nominated in the most recent proxy statement of the Company; or (d) a liquidation or dissolution of the Company or the sale of all or substantially all of the Company's assets.
A-1

 SUPPLEMENT B
1.
Purpose. The provisions of this Supplement B shall apply to any deferrals made under the 1999 Plan. To the extent these provisions are inconsistent with any other provision of the Plan the provisions herein shall govern.

2.
Distributions. Any distribution which has not commenced by November 1, 2002 will be modified by the Administrative Committee in accordance with Section 5.01 of the Plan.
B-1

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Exhibit 4.6
AON DEFERRED COMPENSATION PLAN
 TABLE OF CONTENTS
 SECTION 1 Definitions
 SECTION 2 Eligibility
 SECTION 3 Election To Defer
 SECTION 4 Deferred Compensation Amounts and Investment Elections
 SECTION 5 Method of Distribution
 SECTION 6 Miscellaneous
 SUPPLEMENT A
 SUPPLEMENT B
 
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 Exhibit 5
June 27, 2003
Aon Corporation
200 East Randolph Street
Chicago, Illinois 60601
Re:
Registration of Common Stock
Ladies and Gentlemen:
        I am Senior Counsel and Assistant Secretary of Aon Corporation (the "Company"). I refer to the Registration Statement on Form S-8 (the "Registration Statement") being filed by the Company with the Securities and Exchange Commission (the "SEC") under the Securities Act of 1933, as amended (the "Securities Act"), relating to the registration of $50,000,000 of deferred compensation obligations (the "Deferred Compensation Obligations") that may be offered to eligible employees of the Company and its subsidiaries pursuant to the Aon Deferred Compensation Plan.
        I am familiar with the proceedings to date with respect to the proposed offering of the Deferred Compensation Obligations and have examined such records, documents and questions of law, and satisfied myself as to such matters of fact, as I have considered relevant and necessary as a basis for this opinion.
        In rendering the opinions expressed below, I have assumed the authenticity of all documents submitted to me as originals and the conformity to the originals of all documents submitted to me as copies. In addition, I have assumed and have not verified the accuracy as to factual matters of each document I reviewed.
        Based on the foregoing, I am of the opinion that:
        1.     The Company is duly incorporated and validly existing under the laws of the State of Delaware.
        2.     The Plan has been duly adopted by the Company.
        3.     The Deferred Compensation Obligations, when issued in accordance with the terms of and subject to the conditions of the Plan, will be duly authorized and validly issued and will constitute the valid and legally binding obligations of the Company, enforceable against the Company in accordance with their terms and the terms of the Plan.
        This opinion letter is limited to the General Corporation Law of the State of Delaware, the laws of the State of Illinois and the federal laws of the United States of America.
        I do not find it necessary for the purposes of this opinion letter to cover, and accordingly I express no opinion as to, the application of the securities or blue sky laws of the various states or the District of Columbia to sales of the Common Stock.
        I hereby consent to the filing of this opinion letter as an Exhibit to the Registration Statement and to all references to me under the caption "Legal Matters" in the Prospectus forming a part of the Registration Statement. In giving such consent, I do not thereby admit that I am within the category of persons whose consent is required by Section 7 of the Securities Act or the related rules and regulations promulgated by the SEC.
Very truly yours,

/s/ Richard E. Barry

Richard E. Barry

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Exhibit 5
 
Exhibit 15
June 24, 2003
Board of Directors and Stockholders
Aon Corporation
        We are aware of the incorporation by reference in the Registration Statement (Form S-8) of Aon Corporation for the registration of $50,000,000 of Aon Deferred Compensation Obligations of our report dated May 9, 2003 relating to the unaudited condensed consolidated interim financial statements of Aon Corporation which is included in its Form 10-Q for the quarter ended March 31, 2003.
/s/ Ernst & Young LLP

 
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Exhibit 23.2
 
 CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS
        We consent to the incorporation by reference in the Registration Statement (Form S-8) of Aon Corporation for the registration of $50,000,000 of Aon Deferred Compensation Obligations of our report dated February 12, 2003 with respect to the consolidated financial statements and the related financial statement schedules of Aon Corporation included in its Annual Report (Form 10-K) for the year ended December 31, 2002 filed with the Securities and Exchange Commission.
/s/ERNST & YOUNG LLP
Chicago, Illinois
June 24, 2003

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 CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS
 
Exhibit 24
POWER OF ATTORNEY
        KNOW ALL MEN BY THESE PRESENTS, that the person whose signature appears below severally constitutes and appoints Patrick G. Ryan, Michael D. O'Halleran, David P. Bolger and Raymond I. Skilling, and each of them, with full power to act without the others, his true and lawful attorneys-in-fact and agents, with full and several power of substitution and resubstitution for the undersigned and in the undersigned's name, place and stead, in any and all capacities, to sign a Registration Statement on Form S-8 (the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), with respect to the registration under the Securities Act of securities and obligations of Aon Corporation with respect to its Deferred Compensation Plan, and any and all amendments and supplements thereto, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, and any and all documents relating to the qualification or registration under state Blue Sky or securities laws of such securities, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as the undersigned might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
        IN WITNESS WHEREOF, the undersigned has signed his name effective as of May 16, 2003.

 	/s/   EDGAR D. JANNOTTA       

Edgar D. Jannotta	

POWER OF ATTORNEY
        KNOW ALL MEN BY THESE PRESENTS, that the person whose signature appears below severally constitutes and appoints Patrick G. Ryan, Michael D. O'Halleran, David P. Bolger and Raymond I. Skilling, and each of them, with full power to act without the others, his true and lawful attorneys-in-fact and agents, with full and several power of substitution and resubstitution for the undersigned and in the undersigned's name, place and stead, in any and all capacities, to sign a Registration Statement on Form S-8 (the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), with respect to the registration under the Securities Act of securities and obligations of Aon Corporation with respect to its Deferred Compensation Plan, and any and all amendments and supplements thereto, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, and any and all documents relating to the qualification or registration under state Blue Sky or securities laws of such securities, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as the undersigned might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
        IN WITNESS WHEREOF, the undersigned has signed his name effective as of May 16, 2003.

 	/s/   LESTER B. KNIGHT       

Lester B. Knight	

POWER OF ATTORNEY
        KNOW ALL MEN BY THESE PRESENTS, that the person whose signature appears below severally constitutes and appoints Patrick G. Ryan, Michael D. O'Halleran, David P. Bolger and Raymond I. Skilling, and each of them, with full power to act without the others, his true and lawful attorneys-in-fact and agents, with full and several power of substitution and resubstitution for the undersigned and in the undersigned's name, place and stead, in any and all capacities, to sign a Registration Statement on Form S-8 (the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), with respect to the registration under the Securities Act of securities and obligations of Aon Corporation with respect to its Deferred Compensation Plan, and any and all amendments and supplements thereto, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, and any and all documents relating to the qualification or registration under state Blue Sky or securities laws of such securities, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as the undersigned might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
        IN WITNESS WHEREOF, the undersigned has signed his name effective as of May 16, 2003.

 	/s/   J. MICHAEL LOSH       

J. Michael Losh	

POWER OF ATTORNEY
        KNOW ALL MEN BY THESE PRESENTS, that the person whose signature appears below severally constitutes and appoints Patrick G. Ryan, Michael D. O'Halleran, David P. Bolger and Raymond I. Skilling, and each of them, with full power to act without the others, his true and lawful attorneys-in-fact and agents, with full and several power of substitution and resubstitution for the undersigned and in the undersigned's name, place and stead, in any and all capacities, to sign a Registration Statement on Form S-8 (the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), with respect to the registration under the Securities Act of securities and obligations of Aon Corporation with respect to its Deferred Compensation Plan, and any and all amendments and supplements thereto, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, and any and all documents relating to the qualification or registration under state Blue Sky or securities laws of such securities, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as the undersigned might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
        IN WITNESS WHEREOF, the undersigned has signed his name effective as of May 16, 2003.

 	/s/   R. EDEN MARTIN       

R. Eden Martin	

POWER OF ATTORNEY
        KNOW ALL MEN BY THESE PRESENTS, that the person whose signature appears below severally constitutes and appoints Patrick G. Ryan, Michael D. O'Halleran, David P. Bolger and Raymond I. Skilling, and each of them, with full power to act without the others, his true and lawful attorneys-in-fact and agents, with full and several power of substitution and resubstitution for the undersigned and in the undersigned's name, place and stead, in any and all capacities, to sign a Registration Statement on Form S-8 (the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), with respect to the registration under the Securities Act of securities and obligations of Aon Corporation with respect to its Deferred Compensation Plan, and any and all amendments and supplements thereto, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, and any and all documents relating to the qualification or registration under state Blue Sky or securities laws of such securities, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as the undersigned might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
        IN WITNESS WHEREOF, the undersigned has signed his name effective as of May 16, 2003.

 	/s/   ROBERT S. MORRISON       

Robert S. Morrison	

POWER OF ATTORNEY
        KNOW ALL MEN BY THESE PRESENTS, that the person whose signature appears below severally constitutes and appoints Patrick G. Ryan, Michael D. O'Halleran, David P. Bolger and Raymond I. Skilling, and each of them, with full power to act without the others, his true and lawful attorneys-in-fact and agents, with full and several power of substitution and resubstitution for the undersigned and in the undersigned's name, place and stead, in any and all capacities, to sign a Registration Statement on Form S-8 (the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), with respect to the registration under the Securities Act of securities and obligations of Aon Corporation with respect to its Deferred Compensation Plan, and any and all amendments and supplements thereto, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, and any and all documents relating to the qualification or registration under state Blue Sky or securities laws of such securities, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as the undersigned might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
        IN WITNESS WHEREOF, the undersigned has signed his name effective as of May 16, 2003.

 	/s/   RICHARD C. NOTEBAERT       

Richard C. Notebaert	

POWER OF ATTORNEY
        KNOW ALL MEN BY THESE PRESENTS, that the person whose signature appears below severally constitutes and appoints Patrick G. Ryan, David P. Bolger and Raymond I. Skilling, and each of them, with full power to act without the others, his true and lawful attorneys-in-fact and agents, with full and several power of substitution and resubstitution for the undersigned and in the undersigned's name, place and stead, in any and all capacities, to sign a Registration Statement on Form S-8 (the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), with respect to the registration under the Securities Act of securities and obligations of Aon Corporation with respect to its Deferred Compensation Plan, and any and all amendments and supplements thereto, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, and any and all documents relating to the qualification or registration under state Blue Sky or securities laws of such securities, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as the undersigned might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
        IN WITNESS WHEREOF, the undersigned has signed his name effective as of May 16, 2003.

 	/s/   MICHAEL D. O'HALLERAN       

Michael D. O'Halleran	

POWER OF ATTORNEY
        KNOW ALL MEN BY THESE PRESENTS, that the person whose signature appears below severally constitutes and appoints Patrick G. Ryan, Michael D. O'Halleran, David P. Bolger and Raymond I. Skilling, and each of them, with full power to act without the others, his true and lawful attorneys-in-fact and agents, with full and several power of substitution and resubstitution for the undersigned and in the undersigned's name, place and stead, in any and all capacities, to sign a Registration Statement on Form S-8 (the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), with respect to the registration under the Securities Act of securities and obligations of Aon Corporation with respect to its Deferred Compensation Plan, and any and all amendments and supplements thereto, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, and any and all documents relating to the qualification or registration under state Blue Sky or securities laws of such securities, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as the undersigned might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
        IN WITNESS WHEREOF, the undersigned has signed his name effective as of May 16, 2003.

 	/s/   JOHN W. ROGERS, JR.       

John W. Rogers, Jr.	

POWER OF ATTORNEY
        KNOW ALL MEN BY THESE PRESENTS, that the person whose signature appears below severally constitutes and appoints Patrick G. Ryan, Michael D. O'Halleran, David P. Bolger and Raymond I. Skilling, and each of them, with full power to act without the others, his true and lawful attorneys-in-fact and agents, with full and several power of substitution and resubstitution for the undersigned and in the undersigned's name, place and stead, in any and all capacities, to sign a Registration Statement on Form S-8 (the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), with respect to the registration under the Securities Act of securities and obligations of Aon Corporation with respect to its Deferred Compensation Plan, and any and all amendments and supplements thereto, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, and any and all documents relating to the qualification or registration under state Blue Sky or securities laws of such securities, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as the undersigned might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
        IN WITNESS WHEREOF, the undersigned has signed his name effective as of May 16, 2003.

 	/s/   P.J. KALFF       

P.J. Kalff	

POWER OF ATTORNEY
        KNOW ALL MEN BY THESE PRESENTS, that the person whose signature appears below severally constitutes and appoints Patrick G. Ryan, Michael D. O'Halleran, David P. Bolger and Raymond I. Skilling, and each of them, with full power to act without the others, his true and lawful attorneys-in-fact and agents, with full and several power of substitution and resubstitution for the undersigned and in the undersigned's name, place and stead, in any and all capacities, to sign a Registration Statement on Form S-8 (the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), with respect to the registration under the Securities Act of securities and obligations of Aon Corporation with respect to its Deferred Compensation Plan, and any and all amendments and supplements thereto, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, and any and all documents relating to the qualification or registration under state Blue Sky or securities laws of such securities, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as the undersigned might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
        IN WITNESS WHEREOF, the undersigned has signed his name effective as of May 16, 2003.

 	/s/   GEORGE A. SCHAEFER       

George A. Schaefer	

POWER OF ATTORNEY
        KNOW ALL MEN BY THESE PRESENTS, that the person whose signature appears below severally constitutes and appoints Patrick G. Ryan, Michael D. O'Halleran, David P. Bolger and Raymond I. Skilling, and each of them, with full power to act without the others, his true and lawful attorneys-in-fact and agents, with full and several power of substitution and resubstitution for the undersigned and in the undersigned's name, place and stead, in any and all capacities, to sign a Registration Statement on Form S-8 (the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), with respect to the registration under the Securities Act of securities and obligations of Aon Corporation with respect to its Deferred Compensation Plan, and any and all amendments and supplements thereto, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, and any and all documents relating to the qualification or registration under state Blue Sky or securities laws of such securities, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as the undersigned might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
        IN WITNESS WHEREOF, the undersigned has signed her name effective as of May 16, 2003.

 	/s/   CAROLYN Y. WOO       

Carolyn Y. Woo	

POWER OF ATTORNEY
        KNOW ALL MEN BY THESE PRESENTS, that the person whose signature appears below severally constitutes and appoints Patrick G. Ryan, Michael D. O'Halleran, David P. Bolger and Raymond I. Skilling, and each of them, with full power to act without the others, his true and lawful attorneys-in-fact and agents, with full and several power of substitution and resubstitution for the undersigned and in the undersigned's name, place and stead, in any and all capacities, to sign a Registration Statement on Form S-8 (the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), with respect to the registration under the Securities Act of securities and obligations of Aon Corporation with respect to its Deferred Compensation Plan, and any and all amendments and supplements thereto, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Securities and Exchange Commission, and any and all documents relating to the qualification or registration under state Blue Sky or securities laws of such securities, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as the undersigned might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or their or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.
        IN WITNESS WHEREOF, the undersigned has signed his name effective as of May 16, 2003.

 	/s/   ANDREW J. MCKENNA       

Andrew J. McKenna