Exhibit 12(a)

                             Aon Corporation and Consolidated Subsidiaries
                               Combined With Unconsolidated Subsidiaries
                           Computation of Ratio of Earnings to Fixed Charges


                                            First Quarter Ended
                                                 March 31,              Years Ended December 31,
                                           ----------------- ------------------------------------------
 (millions except ratios)                    1999     1998    1998     1997    1996     1995     1994
                                           -------- -------- ------- -------- -------  ------- --------
                                                                              
 Income from continuing operations
    before provision for income taxes (1)   $   96   $  238  $  931   $  542  $  446   $  458   $  397

 ADD BACK FIXED CHARGES:

    Interest on indebtedness                    21       20      87       70      45       56       46

    Interest on ESOP                             -        1       2        3       4        5        6

    Portion of rents representative of
      interest factor                           13       11      51       44      29       21       29

                                            -------  ------- -------  ------- -------  -------  -------
         INCOME AS ADJUSTED                 $  130   $  270  $ 1,071  $  659  $  524   $  540   $  478
                                            =======  ======= =======  ======= =======  =======  =======


 FIXED CHARGES:

    Interest on indebtedness                $   21   $   20  $   87   $   70  $   45   $   56   $   46

    Interest on ESOP                             -        1       2        3       4        5        6

    Portion of rents representative of
       interest factor                          13       11      51       44      29       21       29

                                            -------  ------- -------  ------- -------  -------  -------
         TOTAL FIXED CHARGES                $   34   $   32  $  140   $  117  $   78   $   82   $   81
                                            =======  ======= =======  ======= =======  =======  =======

 RATIO OF EARNINGS TO FIXED CHARGES            3.8      8.5     7.6      5.6     6.7      6.6      5.9
                                            =======  ======= =======  ======= =======  =======  =======

 RATIO OF EARNINGS TO FIXED CHARGES (2)        8.6                       7.1     7.9
                                            =======                   ======= =======

<FN>
(1)   Income from continuing  operations  before  provision for income taxes and
      minority  interest  includes special charges of $163 million for the first
      quarter  ended  March 31, 1999 and $172  million  and  $90 million for the
      years ended December 31, 1997 and 1996, respectively.

(2)   The  calculation  of this ratio of earnings to fixed charges  reflects the
      exclusion of special  charges from the income from  continuing  operations
      before  provision  for income taxes  component for the first quarter ended
      March  31,  1999 and for the  years  ended  December  31,  1997 and  1996,
      respectively.
</FN>