X0304 5 2011-12-31 0 0 1 0000315293 AON CORP AON 0001023262 KNIGHT LESTER B AON CORPORATION - CORPORATE LAW DEPT 200 EAST RANDOLPH STREET, 8TH FLOOR CHICAGO IL 60601 1 0 0 0 Common Stock 2011-05-06 5 G 0 19997 0 D 35003 I By Wife Common Stock 2011-12-01 4 M 0 L 5082 A 9209 D Common Stock 25000 I By Family Partnership Deferred Stock Unit Award (Right to Receive) 2011-12-01 4 M 0 L 5082 0 D 2011-12-01 2011-12-01 Common Stock 5082 0 D Due to administrative error, the shares of common stock were not distributed until February 1, 2012. Shares of common stock acquired upon the vesting of a deferred stock unit award. Includes shares of common stock acquired pursuant to dividend reinvestment. The deferred stock unit award converts to shares of common stock on a 1-for-1 basis. /s/ Matthew M. Rice - by Matthew M. Rice pursuant to a power of attorney from Lester B. Knight 2012-02-15