SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                    FORM 8-K

                                 Current Report
                     Pursuant to Section 13 or 15(d) of the
                         Securities Exchange Act of 1934

      Date of report (Date of earliest event reported): December 10, 1997

                                Pegasystems Inc.
               ---------------------------------------------------
               (Exact Name of Registrant as Specified in Charter)

       Massachusetts                  1-11859                   04-2787865
       -------------                  -------                   ----------
(State or Other Jurisdiction     (Commission File            (IRS Employer
     of Incorporation)                Number)             Identification Number)

    101 Main Street, Cambridge, MA                                   02142
    ------------------------------                                   -----
(Address of Principal Executive Offices)                           (Zip Code)

       Registrant's telephone number, including area code: (617) 374-9600



Item 4. Changes in Registrant's Certifying Accountant.

     On December 10, 1997, Pegasystems Inc. (the "Registrant") engaged Arthur
Andersen LLP as the Registrant's independent public accountants.



                                   SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934, the
Registrant has caused this report to be signed on behalf of the undersigned
thereunto duly authorized.

Date: December 15, 1997                        PEGASYSTEMS INC.

                                               By: /s/ Ira Vishner
                                               ------------------------------
                                                   Ira Vishner
                                                   Vice President, Corporate
                                                   Services, Treasurer, Chief
                                                   Financial Officer