X0303 4 2011-05-23 0 0000315293 AON CORP AOC 0001407939 Besio Gregory J C/O AON CORPORATE LAW DEPT 200 EAST RANDOLPH STREET, 8TH FL CHICAGO IL 60601 0 1 0 0 EVP/CAO Common Stock 2011-05-23 4 S 0 7500 51.498 D 43807 D Common Stock 2011-05-23 4 M 0 13468 38.93 A 57275 D Common Stock 2011-05-23 4 S 0 13468 51.50 D 43807 D Common Stock 2011-05-23 4 M 0 7083 38.93 A 50890 D Common Stock 2011-05-23 4 M 0 17186 43.64 A 68076 D Common Stock 2011-05-23 4 S 0 17186 51.586 D 50890 D Common Stock 2011-05-23 4 M 0 22000 40.91 A 72890 D Common Stock 2011-05-23 4 S 0 22000 51.504 D 50890 D Common Stock 6597 I Through Aon Savings Plan and Supplemental Savings Plan Employee Stock Option (Right to Buy) 43.64 2011-05-23 4 M 0 17186 D 2013-05-17 Common Stock 17186 0 D Employee Stock Option (Right to Buy) 38.93 2011-05-23 4 M 0 7083 D 2015-03-19 Common Stock 7083 10274 D Employee Stock Option (Right to Buy) 40.91 2011-05-23 4 M 0 22000 D 2014-03-13 Common Stock 22000 0 D Employee Stock Option (Right to Buy) 38.93 2011-05-23 4 M 0 13468 D 2015-03-19 Common Stock 13468 17357 D 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. 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. 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. Stock option granted pursuant to the Aon Stock Incentive Plan. Includes 151 shares held pursuant to the Aon employee stock purchase plan, and shares acquired pursuant to dividend reinvestment. 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. 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. 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. 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. /s/ Jennifer L. Kraft - by Jennifer L. Kraft pursuant to a power of attorney from Gregory J. Besio 2011-05-25