FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF 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 *   Aigotti Diane 2. Date of Event Requiring Statement (Month/Day/Year) 06/01/2005 3. Issuer Name and Ticker or Trading Symbol AON CORP [AOC] (Last) (First) (Middle) AON CORPORATION - CORPORATE LAW DEPT, 200 EAST RANDOLPH STREET, 8TH FLOOR 4. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) Senior VP & Treasurer 5. If Amendment, Date Original Filed(Month/Day/Year) (Street) CHICAGO, IL 60601 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 Beneficially Owned

1.Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5) Common Stock 0 D   Common Stock 259 I Through Aon Savings Plan and ESOP

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.			SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock Award (Right to Receive)	  (1)(2)	07/16/2009	Common Stock	7,120	$ (3)	D	Â
Stock Award (Right to Receive)	  (4)(5)	03/17/2008	Common Stock	1,925	$ (3)	D	Â
Employee Stock Option (Right to Buy)	  (6)(7)	09/14/2010	Common Stock	10,000	$ 36.6875	D	Â
Employee Stock Option (Right to Buy)	  (6)(8)	04/20/2011	Common Stock	5,000	$ 32.525	D	Â
Employee Stock Option (Right to Buy)	  (6)(9)	04/22/2012	Common Stock	5,000	$ 36.875	D	Â
Employee Stock Option (Right to Buy)	  (6)(10)	03/20/2013	Common Stock	7,500	$ 19.7	D	Â
Employee Stock Option (Right to Buy)	  (11)(12)	07/16/2014	Common Stock	7,120	$ 27.03	D	Â

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Aigotti Diane AON CORPORATION - CORPORATE LAW DEPT 200 EAST RANDOLPH STREET, 8TH FLOOR CHICAGO, IL 60601	Â	Â	  Senior VP & Treasurer	Â

Signatures

/s/ Jennifer L. Kraft - by Jennifer L. Kraft pursuant to a power of attorney from Diane Aigotti		06/09/2005
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 5(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)	Awards will vest in accordance with the Aon Stock Incentive Plan as follows: 100% of the awards will vest on the fifth anniversary of the date of grant.
(2)	The date of grant was July 16, 2004.
(3)	The restricted stock award converts to shares of common stock on a 1-for-1 basis.
(4)	Awards 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)	The date of grant was March 17, 2005.
(6)	Options will vest in accordance with the Aon Stock Incentive Plan as follows: 33% of the options will vest on each of the second and fourth anniversaries of the date of grant, and 34% of the options will vest on the third anniversary of the date of grant.
(7)	The date of grant was September 14, 2000. As of the date of this report, 10,000 options have vested.
(8)	The date of grant was April 20, 2001. As of the date of this report, 5,000 options have vested.
(9)	The date of grant was April 22, 2002. As of the date of this report, 3,350 options have vested.
(10)	The date of grant was March 20, 2003. As of the date of this report, 2,475 options have vested.
(11)	Options will vest in accordance with the Aon Stock Incentive Plan as follows: 100% of the options will vest on the fifth anniversary of the date of grant.
(12)	The date of grant was July 16, 2004.

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