UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the
Securities Exchange Act of 1934

Date of report (Date of earliest event reported): September 30, 2005

Aon Corporation

(Exact Name of Registrant as Specified in Charter)

Delaware	1-7933	36-3051915
(State or Other Jurisdiction	(Commission File Number)	(IRS Employer
of Incorporation)		Identification No.)

200 East Randolph Street, Chicago, Illinois		60601
(Address of Principal Executive Offices)		(Zip Code)

Registrant’s telephone number, including area code: (312) 381-1000

Not Applicable
(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

o Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 1.01. Entry into a Material Definitive Agreement.

On September 30, 2005, Aon Corporation (the “Company”) entered into an amendment (the “Amendment”) with the lenders under its $600 million revolving credit facility (as amended by the Amendment, the “U.S. Facility”).

The Amendment extends the term of the U.S. Facility from three years to five years. As a result, the U.S. Facility will mature on February 3, 2010.

In addition, among other things, the Amendment: (i) eliminates the requirement of a guarantee from Aon Group, Inc. or any other subsidiary; (ii) deletes certain covenants, including those with respect to guarantors and acquisitions; and (iii) revises certain covenants, including those with respect to mergers, dispositions and indebtedness.

The foregoing summary is qualified in its entirety by reference to the Amendment, a copy of which is filed herewith and incorporated herein by reference.

Item 9.01. Financial Statements and Exhibits.

(a)—(b) Not applicable.

Exhibit Number		Description of Exhibit
10.1		Amendment No. 1 to $600,000,000 Three-Year Credit Agreement dated as of February 3, 2005 among Aon Corporation, Citibank, N.A., as Administrative Agent and the lenders listed therein.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	Aon CORPORATION

	By:	/s/ David P. Bolger
		David P. Bolger Executive Vice President, Chief Financial Officer and Chief Administrative Officer

Date: October 5, 2005

EXHIBIT INDEX

Exhibit Number		Description of Exhibit
10.1		Amendment No. 1 to $600,000,000 Three-Year Credit Agreement dated as of February 3, 2005 among Aon Corporation, Citibank, N.A., as Administrative Agent and the lenders listed therein.