On December 16, 2004, the Financial Accounting Standards Board (FASB) unveiled its new accounting standard for calculating the fair value of stock options. FAS123® will force companies to begin treating employee stock options in the same way salaries or cash bonuses are counted.

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Currently, the vast majority of companies calculate stock option cost using the Black-Scholes model. However, FASB's statement suggests that a binomial or "lattice" model is more capable of fully reflecting certain characteristics of employee share options, although it does not state a preference for the binomial or lattice model. FAS123® continues to stress that understanding early exercise behavior by option holders is important to valuing employee stock options properly.

Philip A. Peterson, F.S.A., and Mike Savage, senior vice presidents with Aon Consulting, are available to comment on and explain FAS 123® and its effect on U.S. businesses as well as:

  -- The influence new regulations could have on stock options, stock awards
     and employee stock purchase plans
  -- The implications of using a binomial or "lattice" methodology versus
     the existing Black-Scholes model
  -- The incentive for U.S. companies raising capital abroad to adopt the
     binomial model
  -- Implications on long term incentive plan design for executives


  To arrange an interview with Mr. Peterson or Mr. Savage, contact:
  Dana Sohn, Aon Consulting, +1.312.381.4786, dana_sohn@aon.com
  or
  Bianca Wright, RF Binder Partners, +1.212.994.7545,
  bianca.wright@rfbinder.com


  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.

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, 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.

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SOURCE: Aon Consulting

CONTACT: Dana Sohn of Aon Consulting, +1-312-381-4786,
dana_sohn@aon.com , or Bianca Wright of RF Binder Partners, +1-212-994-7545,
bianca.wright@rfbinder.com

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