Ownership Submission
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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(Print or Type Responses)
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

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
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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