Aon Corporation (NYSE: AOC) today announced the appointment of Steve McGill, 47, as chief executive officer of a new Global Large Corporate business unit that addresses the sophisticated risk management needs of the largest global corporations.

(Logo: http://www.newscom.com/cgi-bin/prnh/20041215/CGW049LOGO )

McGill was chief executive of Jardine Lloyd Thompson Group plc., an international insurance broker. During a brokerage career spanning more than 25 years, he has worked with a wide range of leading global companies. He is a director of the International Insurance Society and deputy president of the Insurance Institute of London.

Aon President and CEO Greg Case said, "As a leading insurance broker, Steve McGill has built a formidable reputation as someone who delivers distinctive value to large corporations. We are delighted to have him join the senior team to help drive this business forward."

Dick Verbeek, chairman of the Global Large Corporate business unit, and Dennis Mahoney, chairman, Aon Limited, said in a joint statement, "Steve's impressive accomplishments in the insurance industry, especially with major corporations, will add significantly to the value that we deliver to our clients."

McGill added, "I am excited by Aon's increasing focus on this segment. There are significant opportunities available to us, and by harnessing Aon's resources, global network and client relationship skills, we can meet the highest expectations of these clients throughout the world."

This business unit includes professional staff in the key financial centers who will work closely with Aon's strong country and regional organizations to provide advice, program design and support for complex risk management needs.

About Aon

Aon Corporation ( http://www.aon.com/ ) is a leading provider of risk management services, insurance and reinsurance brokerage, human capital and management consulting, and specialty insurance underwriting. There are 47,000 employees working in Aon's 500 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 related to future results, or states our intentions, beliefs and expectations or predictions for the future 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: general economic conditions in different countries in which we do business around the world, changes in global equity and fixed income markets that could affect the return on invested assets, fluctuations in exchange and interest rates that could influence revenue and expense, rating agency actions that could affect our ability to borrow funds, funding of our various pension plans, changes in the competitive environment, changes in commercial property and casualty markets and commercial premium rates that could impact revenues, changes in revenues and earnings due to the elimination of contingent commissions, other uncertainties surrounding a new compensation model, the impact of regulatory investigations brought by state attorneys general and state insurance regulators related to our compensation arrangements with underwriters and related issues, the impact of class actions and individual lawsuits including client class actions, securities class actions, derivative actions, and ERISA class actions, the cost of resolution of other contingent liabilities and loss contingencies, and the difference in ultimate paid claims in our underwriting companies from actuarial estimates. 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.

   For more information, contact:
   Sebastian St.John-Clarke
   Aon Press Office, London
   +44(0)20.7.5057201
   sebastian.stjohn-clarke@aon.co.uk

   Dave Van de Walle
   Aon Corporation
   +1-312-381-5028
   dave_vandewalle@aon.com.

Photo: NewsCom: http://www.newscom.com/cgi-bin/prnh/20041215/CGW049LOGO
PRN Photo Desk, photodesk@prnewswire.com

SOURCE: Aon Corporation

CONTACT: Sebastian St.John-Clarke of Aon Press Office, London,
+44-20-7-5057201, sebastian.stjohn-clarke@aon.co.uk or Dave Van de Walle of
Aon Corporation, +1-312-381-5028, dave_vandewalle@aon.com.

Web site: http://www.aon.com/