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 * OHALLERAN MICHAEL D   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) Senior Exec VP (Last) (First) (Middle) AON CORPORATION - CORPORATE LAW DEPT, 200 EAST RANDOLPH STREET, 8TH FLOOR 3. Date of Earliest Transaction (Month/Day/Year) 05/30/2007 (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 05/30/2007   M   177,469 A $ 23.9375 194,538 D   Common Stock 05/30/2007   S   177,469 D $ 42.9483 0 D   Common Stock 05/25/2007   G V 11,020 D (1) 50,281 I Trust for Self Common Stock 05/30/2007   G V 1,725 D (1) 48,556 I Trust for Self Common Stock 05/25/2007   G V 10,721 D (2) 62,002 (3) I Trust for Spouse Common Stock               23,466 (3) I Through Charitable Trust Common Stock               2,268 (3) I By Daughter Common Stock               2,268 (3) I By Son Common Stock               27,266 I Through Aon Savings Plan and ESOP

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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

Employee Stock Option (Right to Buy)

$ 23.9375

05/30/2007

M

177,469

(4)

02/11/2010

Common Stock

177,469

(5)

12,531

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
OHALLERAN MICHAEL D AON CORPORATION - CORPORATE LAW DEPT 200 EAST RANDOLPH STREET, 8TH FLOOR CHICAGO, IL 60601			Senior Exec VP

Signatures

/s/ Jennifer L. Kraft - by Jennifer L. Kraft pursuant to a power of attorney from Michael D. O'Halleran		05/31/2007
**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)	The reporting person made a gift of the shares on the transaction date indicated in column 2.
(2)	The reporting person's spouse made a gift of the shares on the transaction date indicated in column 2.
(3)	The reporting person disclaims beneficial ownership of these shares.
(4)	Vesting occurred in accordance with the terms of the Aon Stock Incentive Plan as follows: thirty-three percent (33%) of the options vested on each of February 11, 2002 and February 11, 2004, and thirty-four percent (34%) of the options vested on February 11, 2003.
(5)	Stock option granted pursuant to the Aon Stock Incentive Plan.

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