Aon today announced it has entered into a letter of intent agreement to acquire Valley Oak Systems of San Ramon, California. Aon expects to consummate the transaction by January 31, 2007.

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

Valley Oak Systems (VOS) is the proven leader of claims management software, services and support for the insurance industry. Its iVOS "one- system" solution includes medical bill review, policy underwriting, case management, billing, and event management capabilities.

VOS will integrate and share data seamlessly with RiskConsole, Aon's state-of-the-art RMIS solution, creating the only end-to-end browser-based offering in the global market. The acquisition of VOS follows the successful integration of Risk Laboratories, LLC (RiskLabs) in 2004.

"We selected Valley Oak Systems because of their exceptional reputation in the market, their dedication to serving clients, and the high caliber of talent within their organization," says Greg Case, Aon president and chief executive officer. "By combining our strengths, we will create a comprehensive risk management information system offering that will have no peer in the marketplace."

Randy Wheeler, founder and chief executive officer of Valley Oak Systems, says, "During the last few years, we've experienced tremendous growth in all aspects of our business. With Aon, we'll continue this strong growth and provide more comprehensive products and services to our clients. Since both of our products are native to the Internet, we'll create the only end-to-end browser-based insurance solution in the global marketplace."

eSolutions' Managing Director, Kathy Burns, says, "With the addition of Valley Oak Systems, Aon will be able to equip its risk professionals with cutting-edge claims administration tools, enabling them to provide the highest level of service and deliver distinctive client value."

About Valley Oak Systems, Inc.

Founded in 1994, Valley Oak Systems has a history of providing high quality software that has enabled its clients to achieve outstanding claims management performance. Due to its client-focused approach, Valley Oak Systems has established itself as an industry leader, and its iVOS claims system has been recognized for its business impact with the 2006 IASA Technology Achievement Award.

About Aon

Aon Corporation (NYSE: AOC) ( 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. Aon has 45,000 employees in 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.

  For more information contact:
  Al Orendorff
  312.381.3153
  al_orendorff@aon.com
  http://www.aon.com/newsroom

  Cynthia Chow
  925-242-4600
  cchow@valleyoak.com

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, our ability to implement restructuring initiatives and other initiatives intended to yield cost savings, our ability to execute the stock repurchase program, our ability to obtain regulatory or legislative changes to permit continuous sales of our supplemental Medicare health product, 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 investigations brought by state attorneys general, state insurance regulators, federal prosecutors, and federal regulators, 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.

First Call Analyst:
FCMN Contact: Al_Orendorff@asc.aon.com

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PRN Photo Desk, photodesk@prnewswire.com

SOURCE: Aon Corporation

CONTACT: Al Orendorff of Aon Corporation, +1-312-381-3153,
al_orendorff@aon.com ; or Cynthia Chow of Valley Oak Systems, +1-925-242-4600,
cchow@valleyoak.com

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