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                                    EXHIBIT 4



                      SECOND AMENDMENT TO RIGHTS AGREEMENT

        This Second Amendment (this "AMENDMENT") to Rights Agreement (the
"RIGHTS AGREEMENT") is effective as of May 29, 2001, by and between MiniMed
Inc., a Delaware corporation (the "COMPANY") and Computershare Investor Services
LLC, (the "RIGHTS AGENT").

                                   BACKGROUND

        A. The Company and Harris Trust Company of California entered into a
Rights Agreement effective as of July 24, 1995 and an Amendment thereto
effective as of May 1, 1999 (collectively the "Rights Agreement"). The Rights
Agent has succeeded to all of the rights and obligations of its Harris Trust
Company of California.

        B. The parties now desire to further amend the Rights Agreement on the
terms set forth below.

                                    AMENDMENT

        NOW, THEREFORE, the parties hereby agree as follows:

        1. All capitalized terms not otherwise defined in this Amendment shall
have the meanings set forth in the Rights Agreement.

        2. Section 1(b) of the Rights Agreement is amended by adding at the end
thereof the following paragraph:

               "Also notwithstanding anything to the contrary in this Section
        1(b), for all purposes of this Agreement (including without limitation
        Section 3(h) and 7(d) but not including the proviso to Section 1(z)(iv))
        Medtronic Inc. ("Medtronic") shall not be deemed to Beneficially Own
        securities of the Company (including without limitation any shares of
        Common Stock of the Company or Rights with respect thereto) that are (x)
        subject to the Agreements to Facilitate Merger (the "Support
        Agreements") to be entered into between Medtronic and certain
        stockholders of the Company concurrently with the Medtronic Merger
        Agreement or (y) Beneficially Owned directly or indirectly by any of the
        parties (other than Medtronic) to the Agreements to Facilitate Merger.
        "Medtronic Merger Agreement" is defined as the Agreement and Plan of
        Merger among Medtronic, the Company and MMI Merger Corp., a wholly-owned
        subsidiary of Medtronic, which the parties propose to enter into at or
        about the time this Amendment is entered into and providing for the
        merger of MMI Merger Corp. into the Company as a result of which the
        Company will become a wholly-owned subsidiary of Medtronic".


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        3. Section 1(k) of the Rights Agreement is amended to read in full as
follows:

               "'Expiration Date' shall mean the earlier of the Effective Time
        (as defined in the Medtronic Merger Agreement) of the merger
        contemplated by the Medtronic Merger Agreement or May 23, 2005."

        4. Section 1(z) of the Rights Agreement is hereby deleted in its
entirety and the following is inserted in lieu thereof:

        "(z) "15% Stockholder" shall mean any Person that, together with all
Affiliates and Associates of such Person, hereafter acquires Beneficial
Ownership of, in the aggregate, a number of Voting Shares of the Company equal
to 1% or more of the Voting Shares then outstanding and thereupon or thereafter
Beneficially Owns 15% or more of the Voting Shares of the Company then
outstanding; provided, however, that the term "15% Stockholder" shall not
include:

               (i) any Person who is the Beneficial Owner of at least 15% of the
        outstanding Common Shares both on the date of this Agreement and at the
        completion of the Company's initial public offering of Common Shares,

               (ii) the Company, any wholly owned Subsidiary of the Company, any
        employee benefit plan of the Company or of a Subsidiary of the Company,
        or any Person holding Voting Shares for or pursuant to the terms of any
        such employee benefit plan;

               (iii) any Person if such Person would not otherwise be a 15%
        Stockholder but for a reduction in the number of outstanding Voting
        Shares resulting from a stock repurchase program or other similar plan
        of the Company or from a self tender offer of the Company, which plan or
        tender offer commenced on or after the date hereof, provided, however,
        that the term "15% Stockholder" shall include such Person from and after
        the first date upon which (A) such Person and or its Affiliates and
        Associates (taken collectively), since the date of the commencement of
        such plan or tender offer, shall have acquired Beneficial Ownership of,
        in the aggregate, a number of Voting Shares of the Company equal to 1%
        or more of the Voting Shares of the Company then outstanding and (B)
        such Person, together with all Affiliates and Associates of such Person,
        shall Beneficially Own 15% or more of the Voting Shares of the Company
        then outstanding, or

               (iv) Medtronic, but only to the extent that it acquires or is
        deemed to acquire Beneficial Ownership of any Voting Shares by entering
        into the Medtronic Merger Agreement or by consummating the transactions
        contemplated thereby or by entering into the Support Agreements or by
        consummating the transactions contemplated thereby, provided, however,
        that the term "15% Stockholder" shall include Medtronic from and after
        the first date after entering into the Medtronic Merger Agreement or the
        Support Agreements upon which (A) Medtronic and/or its Affiliates and
        Associates (taken collectively) shall have acquired Beneficial Ownership
        of, in the aggregate, a number of Voting Shares of the Company equal to
        1% or more of the Voting Shares of the Company then outstanding and (B)
        Medtronic, together with all of its Affiliates and Associates,


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        shall Beneficially Own 15% or more of the Voting Shares of the Company
        then outstanding.

Solely for purposes of the proviso to Section 1(z)(iv), Medtronic shall be
deemed to Beneficially Own securities of the Company that are subject to the
Support Agreements or Beneficially Owned directly or indirectly by any of the
parties (other than Medtronic) to the Support Agreements. In calculating the
percentage of the outstanding Voting Shares that are Beneficially Owned by a
Person for purposes of this subsection (z), Voting Shares that are Beneficially
Owned by such Person shall be deemed outstanding, and Voting Shares that are not
Beneficially Owned by such Person and that are subject to issuance upon the
exercise or conversion of outstanding conversion rights, exchange rights, rights
(other than Rights), warrants or options shall not be deemed outstanding. Any
determination made by the Board of Directors as to whether any Person is or is
not a 15% Stockholder shall be conclusive and binding upon all holders of
Rights."

        5. There is hereby added to the Rights Agreement a new Section 35 which
will read in full as follows:

               "Notwithstanding anything else in this Agreement to the contrary,
        on the Expiration Date all Rights shall, without any payment by the
        Company or Medtronic, expire with neither the Company nor Medtronic
        having any obligations under, and no persons having any rights under,
        this Agreement except for the payment of fees and expenses and
        indemnification, if any, to which the Rights Agent is entitled under
        this Agreement".

        6. The Summary of Rights referred to in Section 3(d) of the Rights
Agreement shall be revised by the Company to reflect the changes made by this
Amendment prior to its being sent out as required by Section 3(d).

        7. This Amendment shall be governed by and construed in accordance with
the laws of the State of Delaware applicable to contracts made and to be
performed entirely within such State.

        8. This Amendment may be executed in any number of counterparts and each
of such counterparts shall for all purposes be deemed to be an original, and all
such counterparts shall together constitute but one and the same instrument.


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        IN WITNESS WHEREOF, the Corporation and the Rights Agent have executed
this Amendment effective as of the date first above written.

                                       THE CORPORATION:

                                       MINIMED INC.


                                       By:    /s/ Terrance H. Gregg
                                              ---------------------------------
                                       Name:  Terrance H. Gregg
                                              ---------------------------------
                                       Title: President
                                              ---------------------------------


                                       THE RIGHTS AGENT:

                                       COMPUTERSHARE INVESTOR SERVICES LLC.


                                       By:    /s/ Kenneth J. Vlk
                                              ---------------------------------
                                       Name:  Kenneth J. Vlk
                                              ---------------------------------
                                       Title: Relationship Manager
                                              ---------------------------------




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