X0202 4 2006-05-18 0 0000315293 AON CORP AOC 0001145037 RYAN PATRICK G C/O AON CORPORATE LAW DEPARTMENT 8TH FLOOR, 200 EAST RANDOLPH DRIVE CHICAGO IL 60601 1 1 0 0 Executive Chairman Common Stock 2006-05-18 4 S 0 100 35.45 D 8732494 D Common Stock 2006-05-18 4 S 0 900 35.48 D 8731594 D Common Stock 2006-05-18 4 S 0 4700 35.81 D 8726894 D Common Stock 2006-05-18 4 S 0 21500 35.80 D 8705394 D Common Stock 2006-05-18 4 S 0 400 35.83 D 8704994 D Common Stock 2006-05-18 4 S 0 1000 35.82 D 8703994 D Common Stock 2006-05-18 4 S 0 7800 35.76 D 8696194 D Common Stock 2006-05-18 4 S 0 4100 35.77 D 8692094 D Common Stock 2006-05-19 4 S 0 100 36.21 D 8691994 D Common Stock 2006-05-19 4 S 0 100 36.22 D 8691894 D Common Stock 2006-05-19 4 S 0 100 36.27 D 8691794 D Common Stock 2006-05-19 4 S 0 2400 36.28 D 8689394 D Common Stock 2006-05-19 4 S 0 500 36.30 D 8688894 D Common Stock 2006-05-19 4 S 0 600 36.31 D 8688294 D Common Stock 2006-05-19 4 S 0 300 36.32 D 8687994 D Common Stock 2006-05-19 4 S 0 300 36.33 D 8687694 D Common Stock 2006-05-19 4 S 0 700 36.34 D 8686994 D Common Stock 2006-05-19 4 S 0 400 36.35 D 8686594 D Common Stock 2006-05-19 4 S 0 200 36.37 D 8686394 D Common Stock 2006-05-19 4 S 0 200 36.38 D 8686194 D Common Stock 2006-05-19 4 S 0 200 36.39 D 8685994 D Common Stock 2006-05-19 4 S 0 100 36.40 D 8685894 D Common Stock 2006-05-19 4 S 0 300 36.41 D 8685594 D Common Stock 2006-05-19 4 S 0 100 36.42 D 8685494 D Common Stock 2006-05-19 4 S 0 200 36.45 D 8685294 D Common Stock 2006-05-19 4 S 0 200 36.46 D 8685094 D Common Stock 2006-05-19 4 S 0 100 36.47 D 8684994 D Common Stock 2006-05-19 4 S 0 100 36.53 D 8684894 D Common Stock 2006-05-19 4 S 0 400 36.54 D 8684494 D Common Stock 2006-05-19 4 S 0 200 36.55 D 8684294 D The sales reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 25, 2005. Form 3 of 4 /s/ Patrick G. Ryan 2006-05-22