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                                                                   EXHIBIT 10.21

                                 THIRD AMENDMENT
                            TO THE ADESA CORPORATION
                     SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN


     WHEREAS, ADESA Corporation, Indianapolis, Indiana (the "Sponsoring
Employer") has adopted the ADESA Corporation Supplemental Executive Retirement
Plan (the "Plan") for the benefit of a select group management or highly
compensated employees; and

     WHEREAS, pursuant to Section 7.1 of the Plan, the Sponsoring Employer has
reserved the right to amend the Plan by action of its Board of Directors, and
pursuant to such right the Sponsoring Employer has previously amended the Plan
by a First Amendment, effective in part as of October 1, 2001 and in part as of
November 1, 2001, and by a Second Amendment, effective January 1, 2002; and

     WHEREAS, the Board of Directors of the Sponsoring Employer has approved and
adopted the Third Amendment to the Plan to: (1) redefine the Plan's eligibility
provision; (2) increase by two percent (2%) the employer contributions under the
Plan; and (3) modify the Plan's provisions which trigger an automatic
distribution of accrued benefits under the Plan; and

     WHEREAS, the Board of Directors of the Sponsoring Employer has authorized
and directed the President of the Sponsoring Employer to execute the Third
Amendment to the Plan;

     NOW, THEREFORE, the Plan is hereby amended, effective January 1, 2003, as
follows:

     I.   Section 1.5 is restated in its entirety to read as follows:

          "Change in Control of the Company" means:

          (a)   any merger, consolidation, share exchange or other combination
                or reorganization involving the Company, with respect to which
                the Company is not the surviving entity;

          (b)   any sale, lease, exchange, transfer, or other disposition of all
                or any substantial part of the assets of the Company;

          (c)   any acquisition or agreement to acquire by any person or entity
                (other than an employee pension benefit plan sponsored by the
                Company), directly or indirectly, beneficial ownership of fifty
                percent (50%) or more of the outstanding voting stock of the
                Company;

          (d)   a majority of the Board or a majority of the shareholders of the
                Company approve, adopt, agree to recommend, or accept any
                agreement, contract, offer, or other arrangement providing for
                any of the transactions described above;

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          (e)   the consummation of any series of transactions which result in
                any of the transactions described above; or

          (f)   any other set of circumstances which the Board determines, in
                its sole discretion, constitutes a Change in Control of the
                Company.

          Notwithstanding the foregoing, a Change in Control of the Company
          shall not occur as a result of the issuance of stock by the Company in
          connection with any public offering of its stock."

     II.  Section 2.1 is hereby amended in its entirety to read as follows:

          "2.1  INITIAL ELIGIBILITY. An Eligible Employee will become a
          Participant in the Plan as of the date specified by the Chairman of
          the Company's Board of Directors. For purposes of this Plan, an
          Eligible Employee is: (a) any Employee of the Company or any of its
          Subsidiaries who (i) is classified as a Vice-President or above, and
          (ii) has been approved for participation in the Plan by the Chairman
          of the Company's Board of Directors; and (b) any Employee of the
          Company or any of its Subsidiaries who (i) is not classified as a
          Vice-President or above, and (ii) was designated as an Eligible
          Employee by the Chairman of the Company's Board of Directors, and
          became a Participant in the Plan, prior to January 1, 2003.

     III. Section 2.2 is restated in its entirety to read as follows:

          "2.2  CHANGE IN ELIGIBILITY. A Participant may be removed as an active
          Participant by the Chairman of the Company's Board of Directors
          effective as of any date. Upon such removal, the Participant shall
          become an inactive Participant. As an inactive Participant, he or she
          will not be entitled to make any further Participant Deferral
          Contributions to the Plan, nor shall he or she be entitled to receive
          any further Employer contributions to the Plan on his or her behalf.
          Both the Deferral Account and the Employer Contribution Account of an
          inactive Participant shall, however, continue to be credited with the
          investment earnings of the Trust which are attributable to such
          accounts as provided in Section 3.4. The Administrator will maintain
          such accounts of an inactive Participant until the occurrence of an
          event which entitles such Participant to receive a distribution of
          such accounts under Section 5.1, at which time such accounts will be
          distributed as provided in Article V."

     IV.  Subsection 3.3(a), as previously amended by the Second Amendment
          effective January 1, 2002, is hereby amended in its entirety,
          effective January 1, 2003, to read as follows:

          "(a)  GENERAL PROVISIONS. For each Plan Year commencing prior to
                January 1, 2003 an Employer shall make the contributions
                required by this Section 3.3 pursuant to the provisions of the
                Plan in effect from time to time prior to January 1, 2003.

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                For each Plan Year commencing on or after January 1, 2003, an
                Employer shall make a contribution for each Participant in its
                employ on the first day of the applicable Plan Year in an amount
                equal to the sum of seven percent (7%) of the Participant's Base
                Salary up to the Code Section 401(a)(17) compensation limit in
                effect for the applicable Plan Year, plus eleven percent (11%)
                of the Participant's Base Salary in excess of the Code Section
                401(a)(17) compensation limit in effect for the applicable Plan
                Year.

                Commencing with the calendar month next following the calendar
                month in which a Participant completes one hundred and twenty
                (120) months of combined participation in this Plan and the
                predecessor to this Plan (the Insured Security Option Plan, or
                ISOP, maintained by the Company between March 6, 1998, and March
                5, 2001), the foregoing seven percent (7%) shall be increased to
                ten percent (10%) and the foregoing eleven percent (11%) shall
                be increased to fourteen percent (14%). For example, if a
                Participant completes 120 months of combined plan participation
                on March 5, 2008, then the employer contribution under this
                subsection for the 2008 Plan Year will be equal to the sum of
                (i) 7% of his Base Salary for the first three months of 2008, up
                to one-fourth of the Code Section 401(a)(17) compensation limit
                in effect for 2008, plus 11% of such Base Salary in excess of
                such prorated compensation limit, and (ii) 10% of his Base
                Salary for the last nine months of 2008, up to three-fourths of
                such compensation limit, plus 14% of such Base Salary in excess
                of such prorated compensation limit."

     V.   Section 5.1 is restated in its entirety to read as follows:

          "5.1  TIME OF PAYMENT OF BENEFITS. All amounts credited to the
          Deferral and Employer Contribution Accounts of an active or inactive
          Participant shall be, or shall commence to be, distributed to or for
          the benefit of such Participant (or his or her designated beneficiary
          in the event of the Participant's death) within a reasonable period
          following the earlier of (i) the date the Participant terminates
          employment with ALLETE, Inc., and all of its affiliated companies, or
          (ii) the effective date of any Change in Control of the Company."

     IN WITNESS WHEREOF, the President of the Sponsoring Employer has caused
this amendment to be executed this 20th day of December, 2002, but effective as
of January 1, 2003.

                                            ADESA CORPORATION


                                            By   /s/ Brian J. Warner
                                              --------------------------------
                                              Brian J. Warner, President

ATTEST:

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  /s/ Karen C. Turner
--------------------------------
Karen C. Turner, Secretary

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