FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * MAHONEY DENNIS L   2. Issuer Name and Ticker or Trading Symbol AON CORP [AOC] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) Aon Limited - Chairman/CEO (Last) (First) (Middle) AON CORPORATION - CORPORATE LAW DEPT, 200 EAST RANDOLPH STREET, 8TH FLOOR 3. Date of Earliest Transaction (Month/Day/Year) 03/16/2006 (Street) CHICAGO, IL 60601 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 03/17/2006   M(1)   1,865 A (1) 4,519 D   Common Stock 03/17/2006   F(2)   765 D $ 41.365 3,754 D

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Restricted Stock Unit Award (Right to Receive)

(3)

03/16/2006

A

6,271

03/16/2007(4)

03/16/2009

Common Stock

6,271

$ 0

6,271

D

Employee Stock Option (Right to Buy)

$ 41.195

03/16/2006

A

45,515

(5)

03/16/2012

Common Stock

45,515

(6)

45,515

D

Restricted Stock Unit Award (Right to Receive)

(3)

03/17/2006

M

1,865

03/17/2006

03/17/2006

Common Stock

1,865

$ 0

6,527

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
MAHONEY DENNIS L AON CORPORATION - CORPORATE LAW DEPT 200 EAST RANDOLPH STREET, 8TH FLOOR CHICAGO, IL 60601			Aon Limited - Chairman/CEO

Signatures

/s/ Jennifer L. Kraft - Jennifer L. Kraft pursuant to a power of attorney from Dennis L. Mahoney		03/20/2006
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Shares of common stock acquired upon the vesting of a restricted stock award.
(2)	Shares of common stock withheld by the issuer for the payment of withholding taxes in connection with the vesting of a restricted stock award.
(3)	The restricted stock unit award converts to shares of common stock on a 1-for-1 basis.
(4)	Restricted stock units will vest in accordance with the Aon Stock Incentive Plan as follows: 22.22% of the awards will vest on each of the first and second anniversaries of the date of grant, and 55.56% of the awards will vest on the third anniversary of the date of grant.
(5)	Vesting will occur in accordance with the terms of the Aon Stock Incentive Plan as follows: 33.34% of the options will vest on the first anniversary of the date of grant, and 33.33% of the options will vest on each of the second and third anniversaries of the date of grant.
(6)	Stock option granted pursuant to the Aon Stock Incentive Plan.

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