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
5, 1998  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, 1998:

    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-4   333-21237 Offer to exchange Capital Securities of Aon Capital A 
    S-3   333-50607 Pertaining to the  registration  of 369,000 shares of common
                    stock

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
May 5, 1998