EXHIBIT 32.1

                       CERTIFICATION PURSUANT TO 18 U.S.C.
                      SECTION 1350, AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

Pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002, the undersigned certifies that:

      1.    The Annual Report on Form 10-K of SPSS Inc. for the period ended
            December 31, 2004, as amended by that certain Amendment No. 1 to
            Annual Report on Form 10-K and this Amendment No. 2 to Annual Report
            on Form 10-K, as filed with the Securities and Exchange Commission
            on the date hereof (the "Report"), fully complies with the
            requirements of Section 13(a) or 15(d) 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 SPSS Inc.

Date: January 20, 2006                By: /s/ Jack Noonan
                                          -----------------------------------
                                          Jack Noonan
                                          President and Chief Executive Officer