Aon (NYSE: AOC) announces that Aon Human Resources Outsourcing (HRO), a division of Aon Consulting Inc., has formed a strategic alliance agreement with Ultimate Software (NASDAQ: ULTI), a leading provider of Web-based payroll and employee management solutions. This alliance is the latest development in the growth and evolution of Aon HRO, adding payroll solutions for middle market clients as part of its expanding suite of integrated outsourcing services.

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Aon HRO provides clients with comprehensive outsourced health and welfare services, defined benefit and defined contribution solutions, performance measurement and improvement services, hiring and training expertise, leadership, learning and human resources best practices and strategic consulting.

Gary Budzinski, president of Aon HRO, stated, "Ultimate Software's innovative tool, UltiPro Workforce Management, meets all of our requirements for payroll processing and, as an added benefit, has an additional suite of HR features for middle market clients. UltiPro strategically combines benefits administration to payroll services. In one application, we found tremendous capabilities."

UltiPro, which will be available through the Aon HRO global portal, will become an important part of Aon's payroll services, to be managed and delivered by Aon HRO professionals through the group's payroll service center. UltiPro is a flexible and accurate payroll engine that includes custom reporting and online analytics, empowering payroll and finance specialists to find, analyze and output information with little effort and no extra costs.

As part of Aon's end-to-end outsourcing approach, clients will be able to integrate their payroll functions with other HR roles and responsibilities, achieving a more comprehensive HR perspective and a user-friendly approach to payroll processing. To provide clients with this integrated outsourcing strategy, Aon HRO will link its payroll services to benefits administration, employment processing and performance acceptance.

Budzinski said, "It's an important new service in our HR Portfolio. We are dedicated to responding to the challenges and opportunities in the middle market by continuing to build our portfolio of services. Ultimate Software was identified after exploring more than 60 potential providers and 80 different payroll applications. We were committed to finding a premier provider of payroll services and are extremely pleased with our choice."

Marc Scherr, vice chairman and chief operating officer with Ultimate Software, stated, "We're excited that a company of Aon's worldwide stature and leadership position in HR outsourcing has selected UltiPro as a core part of its HRO global portal. It's a huge opportunity, and we're looking forward to a long-term productive relationship. Aon's commitment to quality HR services is closely aligned with Ultimate Software's focus on quality HRMS/payroll product and world-class customer support."

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. The company employs approximately 51,000 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.

Aon Consulting is among the top global human resources consulting firms, with 2003 revenues of $1.185 billion and 7,500 professionals in 140 offices throughout the world. Aon Consulting delivers integrated consulting solutions to help clients with employee benefits, human resources outsourcing, compensation, communication and management consulting.

About Ultimate Software

Ultimate Software is a leader in delivering Web-based payroll and employee management solutions to organizations of all sizes. Ultimate Software's fully integrated, award-winning UltiPro suite of HR software and payroll software enables businesses to manage human resources and payroll strategically and cost-effectively, benefiting everyone in the organization. Ultimate Software offers UltiPro as in-house HR/payroll software or through application hosting.

Headquartered in Weston, Florida, Ultimate Software employs approximately 450 professionals nationwide and services approximately 1,000 customers, representing approximately 3,600 companies and 1.7 million employees across the United States.

Ultimate Software's customers include The Arizona Diamondbacks/Phoenix Suns, Benihana Restaurants, The Container Store, Elizabeth Arden, Omni Hotels and Trammell Crow Residential. Ultimate Software's UltiPro HR and payroll software has won numerous awards and recognition from industry experts.

   Contact:
   Dana Sohn, Aon Consulting, +1.312.381.4786, dana_sohn@aon.com
   or
   Linda Miller, Ultimate Software, +1.954.331.7083,
   linda_miller@ultimatesoftware.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 pending regulatory investigations and related issues, including those related to compensation arrangements with underwriters, 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, and 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. 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.

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SOURCE: Aon Corporation

CONTACT: Dana Sohn of Aon Consulting, +1-312-381-4786,
dana_sohn@aon.com , or Linda Miller of Ultimate Software, +1-954-331-7083,
linda_miller@ultimatesoftware.com

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