Exhibit 10.1

AMENDMENT NO. 2 TO EMPLOYMENT AGREEMENT

This Amendment No. 2 to Employment Agreement (this “Amendment”) attaches to and
forms part of that certain Employment Agreement, effective as of January 1,
2001, and amended as of September 29, 2004 (the “Agreement”), between Aon
Corporation (the “Company”) and Michael D. O’Halleran (the “Executive”).

WHEREAS, the Company and the Executive mutually desire to further amend this
Agreement, as provided in this Amendment;

NOW, THEREFORE, in consideration of the premises and the mutual agreements
contained herein, the parties hereby agree as follows:

1.             The last sentence of Section 1, “Employment,” is hereby deleted
and replaced with the following:

“The term of employment of the Executive pursuant to this Agreement (the
“Employment Period”) shall commence effective as of January 1, 2001 (the
“Effective Date”) and shall end on January 1, 2013.”

2.             Subsection 3(a), “Base Salary,” is hereby deleted in its entirety
and replaced with the following:

“(a) Base Salary.  From April 1, 2006 through the end of the Employment Period,
the Company shall pay to the Executive a base salary at a rate of $1,000,000 per
annum (“Base Salary”), payable in accordance with the Company’s executive
payroll policy.  Such Base Salary shall be subject to increase (but not
decrease) at the discretion of the Company’s Chief Executive Officer and the
Board.”

3.             Subsection 3(b), “Annual Bonus,” is hereby deleted in its
entirety and replaced with the following:

“(b)         Annual Bonus.  For each calendar year of the Employment Period
beginning with 2006, the Executive shall be eligible to participate in the
Senior Officer Incentive Compensation Plan, as approved by Aon’s stockholders in
2001 (the “Plan”) and as amended or replaced from time to time thereafter.  For
each calendar year of the Employment Period beginning with 2006, the Executive’s
target annual bonus shall be 100% of Base Salary and his maximum annual bonus
shall be not less than 200% of Base Salary.”

4.             The following paragraph shall be added at the end of Subsection
3(c), “Stock Awards”:

“Notwithstanding the foregoing, beginning with calendar year 2007 the Executive
shall not be entitled to receive any additional grants of the contractual awards
described immediately above.  In lieu thereof, effective May 18, 2006, the
Organization and Compensation Committee of the Company’s Board of Directors (the
“Committee”) awarded the Executive 83,964 target performance share units

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subject to the terms and conditions set forth herein.  The award provides the
Executive with the opportunity to earn performance share units based on the
achievement of specified pre-tax net income targets for the Global Reinsurance
Segment for the performance period beginning on the first day of the second
quarter of 2006 and ending on December 31, 2008.  Performance shall be measured
on a cumulative basis during the performance period such that, to the extent
that any such targets are not satisfied for any year, the Executive may make up
such shortfall in subsequent years during the performance period.  The earned
performance share units shall be settled and paid in fully vested shares of
common stock of the Company as soon as is practicable after the last day of the
performance period, but not later than March 31, 2009, or such earlier date as
is necessary to comply with Section 409A of the Internal Revenue Code of 1986,
as amended. The unearned performance share units shall be forfeited at such
time.  Other than as set forth herein, the terms and conditions of the Company’s
“Leadership Performance Program” (“LPP”), a sub-plan of the Aon Stock Incentive
Plan as approved and adopted by the Company’s stockholders in 2001, as in effect
on the effective date hereof, shall govern the earning and settlement of the
Executive’s performance share units, including in the event of the Executive’s
termination of employment prior to the last day of the performance period and in
the event of a change in control of the Company.

The Executive shall be eligible to receive awards under the LPP or successor
program(s) for future performance periods in accordance with the terms and
conditions generally applicable to similarly-situated senior executives.

5.             The Agreement is amended by adding after the last section thereof
the following:

“18.         Indemnification.  The Company shall maintain, for the benefit of
the Executive, director and officer liability insurance in form at least as
comprehensive as, and in an amount that is at least equal to, that maintained by
the Company for any other officer or director.  In addition, the Executive shall
be indemnified by the Company against liability as an officer and director of
the Company and any subsidiary or affiliate of the Company to the maximum extent
permitted by applicable law.  The Executive’s rights under this Section 18 shall
continue so long as he may be subject to such liability, whether or not this
Agreement may have terminated prior thereto.

19.           No Mitigation; No Offset.  In no event shall the Executive be
obligated to seek other employment or take any other action by way of mitigation
of the amounts payable to the Executive under any of the provisions of this
Agreement and such amounts shall not be reduced whether or not the Executive
obtains other employment.”

6.             This Amendment is effective as of May 18, 2006.

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IN WITNESS WHEREOF, the parties hereto have executed this Amendment No. 2 to the
Employment Agreement as of May    , 2006.

AON CORPORATION

 

EXECUTIVE:

 

 

 

 

 

 

By:

/s/ Gregory C. Case

 

 

/s/ Michael D. O’Halleran

 

 

 

 

Michael D. O’Halleran

Title:

President and Chief Executive Officer

 

 

 

 

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