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 1100 35.69 D 8766494 D Common Stock 2006-05-18 4 S 0 1400 35.77 D 8765094 D Common Stock 2006-05-18 4 S 0 100 35.87 D 8764994 D Common Stock 2006-05-18 4 S 0 300 35.83 D 8764694 D Common Stock 2006-05-18 4 S 0 2800 35.70 D 8761894 D Common Stock 2006-05-18 4 S 0 4500 35.69 D 8757394 D Common Stock 2006-05-18 4 S 0 100 35.71 D 8757294 D Common Stock 2006-05-18 4 S 0 1700 35.73 D 8755594 D Common Stock 2006-05-18 4 S 0 2400 35.74 D 8753194 D Common Stock 2006-05-18 4 S 0 1700 35.75 D 8751494 D Common Stock 2006-05-18 4 S 0 1600 35.78 D 8749894 D Common Stock 2006-05-18 4 S 0 1500 35.79 D 8748394 D Common Stock 2006-05-18 4 S 0 1800 35.68 D 8746594 D Common Stock 2006-05-18 4 S 0 1600 35.67 D 8744994 D Common Stock 2006-05-18 4 S 0 800 35.72 D 8744194 D Common Stock 2006-05-18 4 S 0 100 35.88 D 8744094 D Common Stock 2006-05-18 4 S 0 700 35.64 D 8743394 D Common Stock 2006-05-18 4 S 0 800 35.61 D 8742594 D Common Stock 2006-05-18 4 S 0 1200 35.56 D 8741394 D Common Stock 2006-05-18 4 S 0 1900 35.54 D 8739494 D Common Stock 2006-05-18 4 S 0 1100 35.51 D 8738394 D Common Stock 2006-05-18 4 S 0 500 35.53 D 8737894 D Common Stock 2006-05-18 4 S 0 1100 35.52 D 8736794 D Common Stock 2006-05-18 4 S 0 1900 35.50 D 8734894 D Common Stock 2006-05-18 4 S 0 700 35.49 D 8734194 D Common Stock 2006-05-18 4 S 0 500 35.47 D 8733694 D Common Stock 2006-05-18 4 S 0 200 35.46 D 8733494 D Common Stock 2006-05-18 4 S 0 300 35.43 D 8733194 D Common Stock 2006-05-18 4 S 0 300 35.44 D 8732894 D Common Stock 2006-05-18 4 S 0 300 35.41 D 8732594 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 2 of 4 /s/ Patrick G. Ryan 2006-05-22