Aon Reports Q4 and Full Year 2006 Results

Fourth quarter revenue grew 7% to $2.4 billion and EPS increased to $0.68

Fourth Quarter Highlights

• Net income from continuing operations, excluding certain items, increased 43% to $0.67 per
  share
• Risk and Insurance Brokerage Services revenue increased 7% to $1.5 billion with organic
  revenue growth of 2%
• Risk and Insurance Brokerage Services pretax margin increased 400 basis points to 12.9%
  and the adjusted pretax margin, excluding certain items, increased 80 basis points to 17.5%
• Consulting revenue increased 8% to $364 million with organic revenue growth of 8%
• Consulting pretax margin increased 160 basis points to 13.5% and the adjusted pretax
  margin, excluding certain items, increased 310 basis points to 15.4%
• Repurchased 11.0 million shares for $390 million
• Concluded the sales of Aon Warranty Group and Construction Program Group

Chicago, United States of America – Aon Corporation (NYSE: AOC) today reported results for
the fourth quarter and full year ended December 31, 2006.

Net income for the fourth quarter was $224 million or $0.68 per share, compared to $224 million
or $0.65 per share for the prior year quarter. Net income from continuing operations was $189
million or $0.58 per share, compared to $102 million or $0.30 per share for the prior year
quarter. Certain items that impacted fourth quarter results and comparisons with the prior year
quarter are detailed in the reconciliations of non-GAAP measures on pages 14 and 15. Net
income from continuing operations, excluding certain items, increased 43% to $0.67 per share
compared to $0.47 per share for the prior year quarter.

“Our fourth quarter results continued to deliver operational improvement as the adjusted pretax
margin increased 270 basis points to 13.9%, with meaningful increases across all operating
segments, even as we make significant investments for the future in new markets, talent and
technology,” said Greg Case, president and chief executive officer. “Our 2006 performance is
fully on track with the first year of our three-year improvement plan, as we made measurable
progress on all three of our key operating metrics. Organic revenue growth was 5%, and on an
adjusted basis, pretax margin improved in each operating segment and net income per share from
continuing operations increased 22%. We concluded the sale of Warranty and certain specialty
Property & Casualty businesses generating approximately $800 million of cash proceeds. Our
balance sheet is strong and we repurchased more than $1 billion of stock in 2006, highlighting
our belief in the underlying strength of Aon and the positive outlook for 2007 and beyond.”

FOURTH QUARTER FINANCIAL SUMMARY

Total revenue increased 7% to $2.4 billion with organic revenue growth of 5%. Risk and
Insurance Brokerage Services revenue increased 7% to $1.5 billion with organic revenue growth
of 2%. Consulting revenue increased 8% to $364 million with organic revenue growth of 8%.
Insurance Underwriting revenue increased 9% to $527 million with organic revenue growth of
9% in Accident & Health and Life (A&H and Life).

Total expenses increased 3% to $2.2 billion due primarily to an unfavorable impact from foreign
exchange of $82 million and a $34 million increase in benefits to policyholders, partially offset
by a $37 million decrease in restructuring expense and an incremental $33 million of estimated
restructuring savings.

Restructuring expense was $86 million in the fourth quarter compared to $123 million for the
prior year. The previously announced three-year restructuring plan is now anticipated to result in
cumulative pretax charges of $365 million. Annualized cost savings are now targeted at
approximately $280 million reflecting further refinement of offshoring and outsourcing
initiatives. An analysis of restructuring related expenses by segment for the fourth quarter and
full year 2006 and 2005 is presented in the attached reconciliation of non-GAAP measures.
Actual and estimated restructuring costs by reporting period, by type, and by geographic region
are detailed on page 16.

Restructuring benefits realized in the fourth quarter and full year 2006 are estimated at $37
million and $119 million, respectively, of which $28 million and $97 million were related to the
brokerage segment, primarily for workforce reduction.

Foreign currency translation losses negatively impacted net income by $0.02 per share
compared to the prior year quarter. In addition, fourth quarter net income included $0.01 per
share of currency hedging losses compared to $0.02 per share of hedging gains in the prior year
quarter.

Effective tax rate on continuing operations was 24.4% for the fourth quarter compared to 28.2%
for the prior year quarter. The effective tax rate for the fourth quarter of 2006 and for 2005 was
impacted by a number of items including adjustments, resolution of certain items and tax credits.
Compared to a normalized effective tax rate of 35%, these items favorably impacted net income
from continuing operations by $0.08 per share in the fourth quarter and $0.04 per share in the
prior year quarter, as highlighted on page 14.

Diluted average shares outstanding were 333.6 million for the fourth quarter compared to
347.5 million in the prior year quarter. During the fourth quarter, the Company repurchased
approximately 11 million shares of common stock for $390 million at an average price of $35.45
per share.

Discontinued operations after-tax income in the fourth quarter was $35 million or $0.10 per
share compared to $122 million or $0.35 per share in the prior year quarter. After-tax income
reflects both the results of operations and the dispositions of Aon Warranty Group (AWG) and
Construction Program Group (CPG) during the fourth quarter of 2006. Income from
discontinued operations in the prior year quarter primarily reflects the gain on sale of Swett &
Crawford of $108 million after-tax or $0.31 per share.