Aon Capital Markets Underwrites Multi-Peril Catastrophe Bond

Business Wire, June 21, 2004

CHICAGO -- Aon Corporation (NYSE:AOC) today announces that its Aon Capital Markets group has underwritten a multi-peril catastrophe bond for Helix 04 Limited. The private placement of $100 million of floating rate notes provides Converium Group with fully collateralized second and subsequent event catastrophe protection for North Atlantic hurricane, U.S. earthquake, Japanese earthquake and European windstorm property catastrophe exposures. Aon Capital Markets was sole manager in underwriting the Rule144A transaction.

Dirk Lohmann, Group CEO of Converium Holding AG, commented "This transaction provides Converium with second and subsequent event protection for our major exposures. The fully collateralized, five-year coverage complements our existing reinsurance program and provides pre-defined reinsurance costs following a major catastrophic event."

"We are delighted to have underwritten this placement on behalf of Converium", said Paul Schultz, president of Aon Capital Markets. "The notes were well received by investors, which demonstrates that the capital markets continue to develop as an additional source of risk transfer capacity."

Coverage provided by the notes is based on modeled losses to a notional portfolio. The notional portfolio was structured to reflect Converium's North Atlantic hurricane, U.S. earthquake, Japanese earthquake and European windstorm exposures. AIR Worldwide provided risk modeling and analysis for this transaction.

The notes issued by Helix 04 Limited priced at LIBOR plus 5.40% with a maturity of five years. Standard & Poor's rated the notes BB .

Aon Capital Markets, Aon's investment banking unit, specializes in raising debt and equity capital for insurance and corporate clients. It provides clients access to a full range of capital and products that are generally not available through traditional insurance and capital markets. Aon Capital Markets has offices in Chicago and London.

Aon Corporation (www.aon.com) is a leading provider of risk management services, insurance and reinsurance brokerage, human capital and management consulting, and specialty insurance underwriting. The company employs approximately 53,000 professionals in its 600 offices in more than 120 countries. Backed by broad resources, industry knowledge and technical expertise, Aon professionals help a wide range of clients develop effective risk management and workforce productivity solutions.

This press release contains 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, exchange rates, rating agency actions, resolution of regulatory issues, pension funding, ultimate paid claims may be different from actuarial estimates and actuarial estimates may change over time, changes in commercial property and casualty markets and commercial premium rates, the competitive environment, the actual costs of resolution of contingent liabilities and other loss contingencies, the heightened level of potential errors and omissions liability arising from placements of complex policies and sophisticated reinsurance arrangements in an insurance market in which insurer reserves are under pressure, 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, is contained in the Company's filings with the Securities and Exchange Commission.