Exhibit 15





Board of Directors and Stockholders
Aon Corporation


We are aware of the incorporation by reference in the Registration Statements of
Aon Corporation ("Aon") described in the following table of our report dated May
1, 1997  relating to the  unaudited  condensed  consolidated  interim  financial
statements of Aon Corporation that are included in its Form 10-Q for the quarter
ended March 31, 1997:

Registration Statement
Form    Number                               Purpose

S-8    33-27984       Pertaining to Aon's savings plan
S-8    33-42575       Pertaining to Aon's stock award plan and stock option plan
S-8    33-59037       Pertaining to Aon's stock award plan and stock option plan
S-3    33-57562       Registration  of Aon's 8% cumulative  perpetual  preferred
                         stock and 6 1/4% cumulative convertible exchangeable 
                         preferred stock
S-4    333-21237      Offer to exchange Capital Securities of Aon Capital A

Pursuant to Rule 436(c) of the  Securities Act of 1933, our report is not a part
of the registration  statements  prepared or certified by accountants within the
meaning of Section 7 or 11 of the Securities Act of 1933.


                                                   /s/ Ernst & Young LLP
                                                   ---------------------
                                                   
                                                     ERNST & YOUNG LLP



Chicago, Illinois
May 1, 1997