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
August  5,  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 June 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
August 5, 1997