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                                  EXHIBIT 4.21


             EIGHTH AMENDMENT TO SAVINGS AND PROFIT SHARING PLAN FOR
                 EMPLOYEES OF FIRST INTERSTATE BANCSYSTEM, INC.

     The Savings and Profit Sharing Plan for Employees of First Interstate
BancSystem, Inc. (the "Plan") is hereby amended as follows, effective
immediately:


                                    ARTICLE 1

     Section 2.1(k)(1) of the Plan is modified to read in its entirety as
follows:

                  (1)      For all purposes of the Plan, except as otherwise
                           specified, Compensation means the base pay, excluding
                           bonuses, overtime, and incentive pay, actually
                           received by a Participant from an Employer during any
                           Plan Year, and including brokers' commissions
                           received after June 30, 1999, all determined prior to
                           any election to reduce his Compensation under Code
                           section 401(k) as described in section 4.3(a) and
                           determined prior to any salary reductions under Code
                           section 125 related to the First Interstate
                           BancSystem of Montana, Inc. Flexible Compensation
                           Program.


                                    ARTICLE 2

     Except as modified herein, all provisions of the Plan shall remain in full
force and effect.

     DATED this 20th day of May, 1999.


                                       FIRST INTERSTATE BANCSYSTEM, INC.


                                       By:  /s/ ROBERT A. JONES
                                            ------------------------------------
                                       Its:  Senior Vice President


                                                                 "Company"