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
November  4, 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 September 30, 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.



                                                  ERNST & YOUNG LLP



Chicago, Illinois
November 4, 1997