Exhibit 99.1

                    Certification of CEO and CFO Pursuant to
                 18 U.S.C. Section 1350, as Adopted Pursuant to
                  Section 906 of the Sarbanes-Oxley Act of 2002

     In connection with the Quarterly Report of Northern Trust Corporation (the
     "Company") on Form 10-Q for the period ending June 30, 2002 as filed with
     the Securities and Exchange Commission on the date hereof (the "Report"),
     William A. Osborn, as Chief Executive Officer of the Company, and Perry R.
     Pero, as Chief Financial Officer of the Company, each hereby certifies,
     pursuant to 18 U.S.C. (S) 1350, as adopted pursuant to (S) 906 of the
     Sarbanes-Oxley Act of 2002, to the best of his knowledge, that:

         (1)    The Report fully complies with the requirements of section
     13(a) of the Securities Exchange Act of 1934; and

         (2)    The information contained in the Report fairly presents, in all
     material respects, the financial condition and results of operations of the
     Company.

     /s/ William A. Osborn
     -------------------------------
         William A. Osborn
         Chief Executive Officer
         August 13, 2002

     /s/ Perry R. Pero
     -------------------------------
         Perry R. Pero
         Chief Financial Officer
         August 13, 2002

     This certification accompanies the Report pursuant to (S) 906 of the
     Sarbanes-Oxley Act of 2002 and shall not be deemed filed by the Company for
     purposes of Section 18 of the Securities Exchange Act of 1934, as amended.