Aon Files Registration Statement in Connection with Previously Issued Convertible Debentures.

Business Editors

CHICAGO--(BUSINESS WIRE)--Jan. 29, 2003

In connection with its November 2002 private offering of convertible debentures, Aon Corporation (NYSE: AOC) today filed a Registration Statement on Form S-3 with the Securities and Exchange Commission (SEC). The Registration Statement was filed in satisfaction of certain registration rights granted to the selling securityholders.

When declared effective by the SEC, the Registration Statement will be available for use by the selling securityholders to resell the previously issued $300 million principal amount 3 1/2% Senior Convertible Debentures due 2012, and the common shares issuable upon conversion of these debentures.

Aon will not receive any proceeds from any resale of the convertible debentures by the selling securityholders or the common stock issuable upon conversion of the convertible debentures.

Aon Corporation (www.aon.com) is a holding company that is comprised of a family of insurance brokerage, consulting and insurance underwriting subsidiaries.

The Registration Statement relating to these securities has been filed with the SEC but has not yet become effective. These securities may not be sold nor may offers to buy be accepted prior to the time the Registration Statement becomes effective. This press release shall not constitute an offer to sell or the solicitation of an offer to buy nor shall there be any sale of these securities in any state in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state. Copies of the preliminary prospectus relating to the offering of the convertible debentures and the common stock issuable upon conversion of the convertible debentures may be obtained by submitting a written request to: Aon Corporation, Corporate Secretary, 200 East Randolph Street, Chicago, Illinois 60601.

This press release may contain certain statements relating to future results, which are forward-looking statements as that term is defined in the Private Securities Litigation Reform Act of 1995. These forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from either historical or anticipated results, depending on a variety of factors. Potential factors that could impact results include the general economic conditions in different countries around the world, fluctuations in global equity and fixed income markets, rating agency actions, the cost and availability of financing, the completion, cost and timing of the capital enhancement plan, changes in commercial property and casualty premium rates, the competitive environment, the actual cost of resolution of contingent liabilities and other loss contingencies, the ultimate impact of the business transformation plan, and the timing and resolution of related insurance and reinsurance issues relating to the events of September 11, 2001. Further information concerning the Company and its business, including factors that potentially could materially affect the Company's financial results, are contained in the Company's filings with the Securities and Exchange Commission.