CHICAGO, May 24, 2004 – Aon Corporation (NYSE: AOC) and Computer Sciences Corporation (NYSE: CSC) have agreed to negotiate the outsourcing of the majority of Aon’s U.S. information technology (IT) infrastructure. The transition to CSC would begin in fall 2004, subject to completing a final contract.

The outsourcing and related consolidation of data centers and other functions, if completed as planned, are designed to produce an estimated $300 million in savings over seven years. CSC’s management of this scope of service is expected to generate in excess of $600 million in revenue for CSC over the life of the agreement, which would cover Aon’s U.S. insurance brokerage and consulting business units.

“CSC has a strong track record for large outsourcing contracts and they will help us achieve an IT outsourcing solution that offers benefits for Aon, our clients and shareholders,” said Patrick G. Ryan, chairman and CEO of Aon Corporation. “CSC also shares Aon’s commitment to a smooth transition for our IT professionals and the processes they manage.”

Functional areas to be outsourced include data centers, telecommunications and data networks, desktop support, related help desk services and various IT support functions. These areas employ approximately 600 people across the United States, including contractors. Most of the affected employees are expected to transition to CSC. Aon will keep responsibility for IT strategy and leadership, architecture and application development and maintenance.

“The outsourcing and related financial benefits will occur in phases,” said Chief Financial Officer David Bolger. “With CSC, we believe we’ve identified an approach that will enable us to maintain or improve client service and meet our administrative needs while contributing to improved overall profitability.”

“We are delighted to have been selected to negotiate a definitive agreement with Aon,” said CSC Chairman and Chief Executive Officer Van B. Honeycutt. “We look forward to applying our experience to help produce business results for this important market leader.”

About Aon

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.

About CSC

Founded in 1959, Computer Sciences Corporation is a leading global IT services company. CSC’s mission is to provide customers in industry and government with solutions crafted to meet their specific challenges and enable them to profit from the advanced use of technology.

With approximately 90,000 employees, CSC provides innovative solutions for customers around the world by applying leading technologies and CSC’s own advanced capabilities. These include systems design and integration; IT and business process outsourcing; applications software development; Web and application hosting; and management consulting. Headquartered in El Segundo, Calif., CSC reported revenue of $14.8 billion for the 12 months ended April 2, 2004. For more information, visit the company’s Web site at www.csc.com.

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.