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                                                                    EXHIBIT 10.1

                          FIRST AMENDMENT AGREEMENT TO
                   SUPPLEMENTAL EXECUTIVE RETIREMENT AGREEMENT


         THIS FIRST AMENDMENT AGREEMENT is made as of this 1st day of October,
1999 between PLEXUS CORP., a Wisconsin corporation (the "Company") and JOHN
NUSSBAUM (the "Employee").

         WHEREAS, the Company and the Employee entered into a Supplemental
Executive Retirement Agreement dated September 19, 1996 (the "Prior Agreement")
and the parties now wish to make certain amendments thereto,

         NOW, THEREFORE, the parties agree as follows:

         1.  Paragraph 1.2 of the Prior Agreement is amended in its entirety
effective as of October 1, 1999, to read as follows:

                           "1.2 `Annual Contribution' means the Amounts
                  referenced in paragraph 2.1."

         2.  Paragraph 2.1 of the Prior Agreement is amended in its entirety,
effective as of October 1, 1999, to read as follows:

                           "2.1 Contributions. The Company has credited to the
                  Employee's Account, starting on the date hereof and continuing
                  through 1998, an Annual Contribution of $90,921.00 and on or
                  about the anniversary dates of this Agreement in 1999 and 2000
                  credited the Employee's Account with an Annual Contribution of
                  $296,279.00. The Company agrees to further credit the
                  Employee's Account with an Annual Contribution of $296,279.00
                  on or about the anniversary date of this Agreement in 2001,
                  provided that the Employee is continuing in the employ of the
                  Company on such date or has entered into a consulting
                  agreement with the Company in the form attached hereto as
                  Exhibit A and made a part hereof and continues in the absence
                  of Disability to comply with the terms thereof."

         3.  Paragraph 3.1 of the Prior Agreement is amended in its entirety
effective as of October 1, 1999, to read as follows:

                           "3.1 Retirement on Termination Other Than for Cause
                  At or After 60. Upon the Employee's retirement or termination
                  other than for Cause at or after attainment of age 60, the
                  Company

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                  shall pay the Employee fifteen (15) annual installments with
                  the first installment to be made within sixty (60) days of the
                  date of such retirement or termination, in an annual amount
                  equal to the sum of the following:

                                    (a) an amount equal to one-fifteenth (1/15)
                           of the cash values in each Policy as of the date the
                           Employee retires or terminates, plus

                                    (b) an amount equal to the increase, if any,
                           in the cash values in each Policy, over those in the
                           immediately prior Policy Year."

         4. Paragraph 3.4 of the Prior Agreement is amended, effective as of
October 1, 1999, to substitute the words "age 60" in place of the words "age 65"
wherever they appear.

         5. The parties reaffirm the Prior Agreement as modified by this First
Amendment Agreement.

         IN WITNESS WHEREOF, the parties have signed this First Amendment
Agreement on the 29th day of December, 2000, but as of the date first set forth
above.

PLEXUS CORP.


By:  Jos. D. Kaufman, Vice President              /s/ John L. Nussbaum
   -------------------------------------       ---------------------------------
                                               JOHN NUSSBAUM

Attest:  Julie Genske, Assistant
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