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 * Meissner Laurel G.   2. Issuer Name and Ticker or Trading Symbol AON CORP [AON] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) SVP & Global Controller (Last) (First) (Middle) AON CORPORATION - CORPORATE LAW DEPT, 200 EAST RANDOLPH STREET, 8TH FLOOR 3. Date of Earliest Transaction (Month/Day/Year) 02/16/2012 (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 02/16/2012   A(1)   15,289 A (1) 16,400 D   Common Stock 02/16/2012   F(2)   4,862 D $ 47.56 11,538 D   Common Stock 02/17/2012   M(3)   899 A (3) 12,437 D   Common Stock 02/17/2012   F(4)   283 D $ 47.62 12,154 D   Common Stock 02/20/2012   M(3)   636 A (3) 12,790 D   Common Stock 02/20/2012   F(4)   201 D $ 47.62 12,589 D

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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)

(5)

02/16/2012

A

2,944

02/16/2013(6)

02/16/2015

Common Stock

2,944

$ 0

2,944

D

Restricted Stock Unit Award (Right to Receive)

(5)

02/17/2012

M

899

02/17/2012

02/17/2012

Common Stock

899

$ 0

1,797

D

Restricted Stock Unit Award (Right to Receive)

(5)

02/20/2012

M

636

02/20/2012

02/20/2012

Common Stock

636

$ 0

1,270

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Meissner Laurel G. AON CORPORATION - CORPORATE LAW DEPT 200 EAST RANDOLPH STREET, 8TH FLOOR CHICAGO, IL 60601			SVP & Global Controller

Signatures

/s/ Matthew M. Rice - Matthew M. Rice pursuant to a power of attorney from Laurel Meissner		02/21/2012
**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)	Represents shares of common stock issued upon the settlement of performance share units originally granted approximately three years ago under the fourth cycle of the Leadership Performance Program ("LPP4") on March 19, 2009. The number of shares issued was determined by the Organization and Compensation Committee of Aon's Board of Directors on February 16, 2012 based upon Aon's performance relative to a cumulative adjusted three year earnings per share target for the period beginning January 1, 2009 and ending December 31, 2011. In accordance with the terms of LPP4, and the achievement of specified growth targets under LPP4, settlement occurred at 124% of the original target value. The terms of LPP4 are more fully described in a Current Report on Form 8-K filed with the SEC on March 25, 2009, and in the plan document filed as Exhibit 10.5 to Aon's Quarterly Report on Form 10-Q for the quarter ended March 31, 2009 filed with the SEC on May 8, 2009.
(2)	Shares of common stock withheld by the issuer for the payment of withholding taxes in connection with the settlement of a performance share unit award.
(3)	Shares of common stock acquired upon the vesting of a restricted stock unit award.
(4)	Shares of common stock withheld by the issuer for the payment of withholding taxes in connection with the vesting of a restricted stock unit award.
(5)	The restricted stock unit award converts to shares of common stock on a 1-for-1 basis.
(6)	The restricted stock unit award will vest in accordance with the terms of the Aon Stock Incentive Plan as follows: 33 1/3% of the awards will vest on each of the first through third anniversaries of the date of grant.
Remarks: Exhibit List: Exhibit 24 - Power of Attorney of Laurel G. Meissner.

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