Aon plc — Director's Dealing 2011

May 25, 2011

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: AON CORP (AOC)
CIK: 0000315293
Period of Report: 2011-05-23

Reporting Person: Besio Gregory J (EVP/CAO)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-05-23	Common Stock	S	7500	$51.498	Disposed	43807	Direct
2011-05-23	Common Stock	M	13468	$38.93	Acquired	57275	Direct
2011-05-23	Common Stock	S	13468	$51.50	Disposed	43807	Direct
2011-05-23	Common Stock	M	7083	$38.93	Acquired	50890	Direct
2011-05-23	Common Stock	M	17186	$43.64	Acquired	68076	Direct
2011-05-23	Common Stock	S	17186	$51.586	Disposed	50890	Direct
2011-05-23	Common Stock	M	22000	$40.91	Acquired	72890	Direct
2011-05-23	Common Stock	S	22000	$51.504	Disposed	50890	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2011-05-23	Employee Stock Option (Right to Buy)	$43.64	M	17186	Disposed	2013-05-17	Common Stock (17186)	Direct
2011-05-23	Employee Stock Option (Right to Buy)	$38.93	M	7083	Disposed	2015-03-19	Common Stock (7083)	Direct
2011-05-23	Employee Stock Option (Right to Buy)	$40.91	M	22000	Disposed	2014-03-13	Common Stock (22000)	Direct
2011-05-23	Employee Stock Option (Right to Buy)	$38.93	M	13468	Disposed	2015-03-19	Common Stock (13468)	Direct

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	6597	Indirect

Footnotes

F1: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $51.49 to $51.52, inclusive. The reporting person undertakes to provide to Aon Corporation, or the Staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F2: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $51.54 to $51.63, inclusive. The reporting person undertakes to provide to Aon Corporation, or the Staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F3: Vesting of the options occurred in accordance with the terms of the Aon Stock Incentive Plan as follows: one-third of the options vested on each of the first through third anniversaries of the date of grant. The date of grant was May 17, 2007.

F4: Stock option granted pursuant to the Aon Stock Incentive Plan.

F5: Includes 151 shares held pursuant to the Aon employee stock purchase plan, and shares acquired pursuant to dividend reinvestment.

F6: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $51.50 to $51.54, inclusive. The reporting person undertakes to provide to Aon Corporation, or the Staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F7: Vesting of the options occurred in accordance with the terms of the Aon Stock Incentive Plan as follows: one-third of the options vested on each of the first through third anniversaries of the date of grant. The date of grant was March 19, 2009.

F8: Vesting of the options occurred in accordance with the terms of the Aon Stock Incentive Plan as follows: one-third of the options vested on each of the first through third anniversaries of the date of grant. The date of grant was March 13, 2008.

F9: Vesting of the options occurred in accordance with the terms of the Aon Stock Incentive Plan as follows: one-third of the options vested on each of the first through third anniversaries of the date of grant. The date of grant was March 19, 2009.