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                                                                   EXHIBIT 10(b)

                              MEMBERSHIP AGREEMENT
                               WITH RESPECT TO THE
                             FIRSTMERIT CORPORATION
                     EXECUTIVE SUPPLEMENTAL RETIREMENT PLAN
                     --------------------------------------

         Membership Agreement, dated this 23rd day of October, 1998, by and
between FIRSTMERIT CORPORATION, an Ohio corporation (the "Employer") and CHARLES
F. VALENTINE, an individual (the "Employee").

                                R E C I T A L S:

         A. The Employer maintains the FirstMerit Corporation Executive
Supplemental Retirement Plan (the "Plan"), a copy of which is attached hereto as
Exhibit A and is incorporated herein by reference, and has selected the Employee
for participation in the Plan.

         B. Section 9.07 of the Plan provides that the Employer and any member
in the Plan may, by written agreement, amend the provisions of the Plan as to
only such member.

         C. The Employer desires that the Employee participate in the Plan,
subject, however, to the modifications set forth in this Agreement and the
Employee desires to accept membership in the Plan subject to such modifications.

         IN CONSIDERATION OF THE FOREGOING, and for good and valuable
consideration, receipt of which is hereby acknowledged, the Employer and
Employee agree as follows:

         1. PARTICIPATION IN THE PLAN. The Employee shall become a Member of the
Plan effective as of October 23, 1998.

         2. EARLY RETIREMENT. Employer and Employee agree that, in the case of
the Employee, the following Section 4.02 shall be substituted for, and shall
apply in lieu of, the Section 4.02 set forth in the Plan:

            "SECTION 4.02 Subject to the provisions of Article X, if the Member
         elects Early Retirement after the third anniversary of the date of this
         Membership Agreement, he shall receive a Monthly Retirement Income
         determined as provided in Section 4.01, without regard to subparagraphs
         (a), (b), (c), (d) or (e) thereof, reduced by three percent for every
         year that the Member's Attained Age on his Retirement Date is less than
         65 as set forth in the following table; PROVIDED, however, that the
         Member's Monthly Retirement Income determined under this Section 4.02,
         without regard to the reductions set forth in subparagraphs (a), (b),
         (c), (d) or (e) below, shall not be less than the Actuarial Equivalent
         of a lump sum benefit payable on the Member's Retirement Date in the
         amount of One Million Four Hundred Twenty Six Thousand Seven Hundred
         Sixty-nine Dollars ($1,426,769.00).


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                                                          RETIREMENT INCOME
                                                          AS A PERCENT OF
                                                          MONTHLY RETIREMENT
                                                          INCOME CALCULATED
                                                          UNDER SECTION 4.01
                                                          WITHOUT REGARD TO
ATTAINED AGE AT                                           SUBPARAGRAPHS (a),
EARLY RETIREMENT                                          (b), (c), (d) OR (e)
                                                        
         60                                                       85%
         61                                                       88%
         62                                                       91%
         63                                                       94%
         64                                                       97%


                     The Member's Monthly Retirement Income calculated under 
         this Section 4.02 shall be further reduced by the following amounts:

                        (a) One hundred percent (100%) of his Primary Social 
         Security Benefit payable at his Retirement Date under the Social
         Security law in effect at that time. If the Member retires prior to age
         62 he shall have his benefits reduced by his Primary Social Security
         payable at age 62, but such reduction shall not occur until the Member
         attains age 62.

                        (b) One hundred percent (100%) of his monthly income 
         payable under the Qualified Plan, calculated in the form of a straight
         life annuity commencing on the Member's Retirement Date.

                        (c) One hundred percent (100%) of his monthly income, 
         if any, payable under the Unfunded Supplemental Benefit Plan,
         calculated in the form of a straight life annuity commencing on the
         Member's Retirement Date.

                        (d) One hundred percent (100%) of his monthly income, 
         if any, payable under any other supplemental retirement plan, program,
         agreement, trust, or annuity provided to the Member by the Employer,
         calculated in the form of a straight life annuity commencing on the
         Member's Retirement Date.

                        (e) One hundred percent (100%) of the benefits received 
         by the Member under any Previous Employer Plan. Amounts payable to the
         Member pursuant to a Previous Employer Plan, including without
         limitation, lump sum distributions, shall be Actuarially Determined as
         a straight life annuity payable in equal monthly installments,
         regardless of the actual form of payment received by the Member. If the
         Member has received a lump sum distribution of all or part of his
         benefit under

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         a Previous Employer Plan prior to his retirement under this Plan, the
         amount of offset shall be Actuarially Determined by assuming that such
         lump sum distribution accumulated interest until the date of the
         Member's retirement under this Plan and by determining the amount of a
         straight life annuity payable to the Member from such adjusted lump sum
         distribution amount."

         3. DEFERRED VESTED BENEFIT. Employer and Employee agree that Section
4.05 of the Plan shall not apply to the Employee.

         4. DEATH BENEFIT. Employer and Employee agree that the third sentence
of Section 5.02 is revised to read as follows:

         "If the Member's death occurs prior to his attainment of age 60, the
         death benefit provided under this Section 5.02 shall be determined
         under Section 4.02 as if the Member had attained age 60 on the date of
         his death."

         5. EFFECT ON PLAN. Except a expressly modified by this Membership
Agreement, all of the provisions of the Plan shall apply to the Employee.

         IN WITNESS WHEREOF, the Employer and Employee have duly executed this
Membership Agreement the day and year above first written.

                                           FirstMerit Corporation


                                           By: /s/ John R. Cochran
                                               -----------------------------
                                               John R. Cochran, Chairman and
                                               Chief Executive Officer

                                                                        EMPLOYER



                                               /S/ Charles F. Valentine
                                               -----------------------------
                                               Charles F. Valentine

                                                                        EMPLOYEE


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