Document:

<PAGE>

                                                                   EXHIBIT 10.24

[LOGO OF AMGEN]      Amendment #2 dated June 22, 2000 to Agreement No. 19990110
--------------------------------------------------------------------------------

Agreement No. 19990110, between Amgen Inc. ("Amgen") and Total Renal Care, Inc.,
including any prior amendments thereto, shall be amended, and for the period
commencing 4/1/2000 shall be restated in its entirety to read in full as stated
below.

This agreement ("Agreement") together with all Appendices attached hereto and
incorporated herein by this reference, between Amgen Inc. ("Amgen") and Total
Renal Care, Inc., including the freestanding dialysis center affiliate(s) listed
on Appendix B, (collectively, "Dialysis Center"), sets forth the terms and
conditions for the purchase of EPOGEN(R) (Epoetin alfa) by Dialysis Center for
the exclusive treatment of dialysis patients.

1.   Term of Agreement. The "Term" of this Agreement shall be defined as April
     1, 2000 ("Commencement Date") through March 31, 2001 ("Termination Date").

2.   Dialysis Center Affiliates. Dialysis Center must provide Amgen with a
     complete list of its dialysis center affiliates ("Affiliates") on or before
     the date this Agreement is executed by Dialysis Center. Affiliates eligible
     to participate under this Agreement shall be listed in Appendix B, and
     shall reflect facilities owned in whole or in part by Dialysis Center or
     for which Dialysis Center provides management or administrative services,
     such services to include the purchase and billing of EPOGEN(R). Additions
     to the dialysis center Affiliates listed on Appendix B may be made pursuant
     to the request of Dialysis Center's corporate headquarters and are subject
     to approval and acknowledgment by Amgen in writing, such approval and
     acknowledgment not to be unreasonably withheld, conditioned or delayed.
     Dialysis Center may delete Affiliates from participation in this Agreement
     at any time, in its sole discretion. Amgen requires reasonable notice
     before the effective date of change (the "Administrative Effective Date")
     for any addition or deletion of Affiliates. [DELETED]; all such purchases
     by Dialysis Center during such period shall constitute "Qualified
     Purchases" under this Agreement and shall be included for purposes of
     eligibility and calculation of each and every discount and incentive
     provided hereunder and in Appendix A, including but not limited to,
     [DELETED] set forth in section 1 of Appendix A, so long as Amgen is not
     obligated to pay the same discount or incentive attributable to the same
     purchases to any person or entity other than Dialysis Center. Amgen
     reserves the right in its reasonable discretion to terminate any Affiliates
     with regard to participation in this Agreement. Termination of any
     Affiliate by Amgen shall be effective (a) immediately in instances in which
     Amgen determines, in its discretion, that such immediate termination is
     required by law or order of any court or regulatory agency or as a result
     of negligence in the use or administration of EPOGEN(R) by such Affiliate;
     or (b) upon 30 days prior written notice to Dialysis Center in all other
     instances; provided, that such termination shall be effective before the
     expiration of such 30 days where Dialysis Center requests or consents to
     such earlier termination.

3.   Own Use. Dialysis Center hereby certifies that EPOGEN(R)purchased hereunder
     shall be for Dialysis Center's "own use", for the exclusive treatment of
     dialysis patients.

4.   Authorized Wholesalers. Dialysis Center must provide Amgen with a complete
     list of its current wholesalers, from whom Dialysis Center intends to
     purchase EPOGEN(R), and must provide the list to Amgen on or before the
     date this Agreement is executed by Dialysis Center's corporate
     headquarters. The list must include the name and complete address of each
     designated wholesaler. Wholesalers designated by Dialysis Center and
     approved by Amgen to participate in this program will be deemed "Authorized
     Wholesalers". A current listing of Dialysis Center's Authorized Wholesalers
     is referenced in Appendix B. Notification of proposed changes to the list
     of Authorized Wholesalers must be provided to Amgen in writing at least 30
     days before the effective date of the proposed change; provided, however,
     that Amgen will use its best efforts to accept a change on fewer than 30
     days' notice. Amgen reserves the right, in its reasonable discretion, to
     reject or terminate, with reasonable notice, any wholesaler with regard to
     participation in this Agreement, so long as (a) Amgen rejects or terminates
     such wholesaler with respect to providing EPOGEN(R) to any and all
     purchasers of EPOGEN(R), or (b) such wholesaler independently requests
     Amgen to remove it as an Authorized Wholesaler for Dialysis Center. Amgen
     also reserves the right, in its reasonable discretion, to accept
     wholesalers with regards to participation in this Agreement, but Amgen
     agrees that it shall accept any Wholesaler designated by Dialysis Center
     which provides EPOGEN(R) to other purchasers approved by Amgen. Dialysis
     Center agrees to request all Authorized Wholesalers to submit product sales
     information to a third-party sales reporting organization designated by
     Amgen.

                                      -1-
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                              Amendment #2 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

5.   Qualified Purchases. Only EPOGEN(R) purchased under this Agreement by
     Dialysis Center through Authorized Wholesalers, as confirmed by Amgen based
     on sales tracking data, will be deemed "Qualified Purchases".

6.   Commitment to Purchase. Dialysis Center agrees to purchase EPOGEN(R) for
     all of its dialysis use requirements for recombinant human erythropoietin,
     and Amgen agrees to supply through Authorized Wholesalers all orders as
     placed by Dialysis Center. Notwithstanding the foregoing, Amgen expressly
     acknowledges and agrees that Dialysis Center may participate in clinical
     trials involving the administration of other products for the management of
     anemia in dialysis patients. Dialysis Center may purchase another brand of
     recombinant human erythropoietin for its dialysis use requirements only for
     the time, and only to the extent, that Amgen has notified Dialysis Center's
     corporate headquarters in writing that Amgen cannot supply EPOGEN(R) within
     and for the time period reasonably required by Dialysis Center. Any such
     notification shall be given by Amgen at least 30 days prior to the date on
     which Amgen will cease supplying EPOGEN(R) to Dialysis Center, unless an
     act or event described in Section 16 below, or an order of a regulatory
     agency or other action arising out of patient safety concerns, requires the
     giving of shorter notice. [DELETED].

7.   Confidentiality. Both Amgen and Dialysis Center agree that this Agreement
     represents and contains confidential information which shall not be
     disclosed to any third party, or otherwise made public, without prior
     written authorization of the other party, except where such disclosure is
     contemplated hereunder or required by law, and then upon notification to
     the other party.

8.   Discounts. Dialysis Center shall qualify for discounts and incentives
     subject to material compliance with the terms and conditions of this
     Agreement as well as the schedules and terms set forth in Appendix A, which
     is incorporated by reference hereto and made a part of this Agreement.
     Discounts in arrears will be paid in the form of a check payable to
     Dialysis Center's corporate headquarters. Discounts in arrears will be
     calculated in accordance with Amgen's discount calculation policies based
     on Qualified Purchases using the [DELETED] as the calculation price, except
     as otherwise provided hereunder. Upon vesting, Amgen will make such
     discounts available within [DELETED], after receipt by Amgen of all
     required data, in a form reasonably acceptable to Amgen, detailing all
     Qualified Purchases during the applicable period. Payment amounts, as
     calculated by Amgen, must equal or exceed $100.00 for the applicable period
     to qualify, and are subject to audit and final determination [DELETED], as
     provided in Appendix A hereto. Subject to the section entitled "Breach of
     Agreement", in the event that Amgen is notified in writing that Dialysis
     Center, and/or any Affiliate(s) (the "Acquired Party") is acquired by
     another entity or a change of control otherwise occurs with respect to any
     Acquired Party, any discounts which may have been earned hereunder for all
     periods preceding such acquisition or change of control shall be paid in
     the form of a check payable to Dialysis Center's corporate headquarters,
     subject to the conditions and requirements described herein. [DELETED].
     Amgen and Dialysis Center agree that, for purposes of determining
     eligibility for and calculation of all discounts and all incentives
     provided in this Agreement (including, without limitation, all discounts
     and incentives as are set forth in Appendix A), a Qualified Purchase of
     EPOGEN(R) shall be deemed made on the date of invoice to Dialysis Center
     from an Authorized Wholesaler. Upon any termination of this Agreement,
     Amgen shall pay to Dialysis Center all discounts and incentives earned by
     Dialysis Center through the date of termination.

                                      -2-
<PAGE>

                              Amendment #2 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

9.   Treatment of Discounts. Dialysis Center agrees that it will properly
     disclose and account for any discount or other reduction in price earned
     hereunder, in whatever form, (i.e. pricing, discount, or incentive) in a
     way that complies with all applicable federal, state, and local laws and
     regulations, including without limitation, Section 1128B(b) of the Social
     Security Act and its implementing regulations. Section 1128B(b) requires
     that a provider of services will properly disclose and appropriately
     reflect the value of any discount or other reduction in price earned in the
     costs claimed or charges made by the provider under a federal health care
     program, as that term is defined in Section 1128B(f). Dialysis Center also
     agrees that it will (a) claim the benefit of such discount received, in
     whatever form, in the fiscal year in which such discount was earned or the
     year after, (b) fully and accurately report the value of such discount in
     any cost reports filed under Title XVIII or Title XIX of the Social
     Security Act, or a state health care program, and (c) provide, upon request
     by the U.S. Department of Health and Human Services or a state agency or
     any other federally funded state health care program, the information
     furnished to Dialysis Center by Amgen concerning the amount or value of
     such discount. Dialysis Center's corporate headquarters agrees that it will
     advise all Affiliates, in writing, of any discount received by Dialysis
     Center's corporate headquarters hereunder with respect to purchases made by
     such Affiliates and that said Affiliates will account for any such discount
     in accordance with the above stated requirements.

10.  Data Collection. Dialysis Center agrees that all data to be provided to
     Amgen pursuant to this Agreement, shall be in a form that does not disclose
     the identity or name of any patient or other patient-identifying
     information such as address, telephone number, or social security number.
     Dialysis Center acknowledges that the data to be supplied to Amgen pursuant
     to this Agreement shall be used to support verification of the discounts
     and incentives referenced herein, as well as for Amgen-sponsored research
     concerning the role of EPOGEN(R) in improving treatment outcomes and
     quality of life of dialysis patients. Dialysis Center shall consistently
     use a unique alpha-numeric code (which shall not be the same as the
     patient's social security number) as a "case identifier" to track the care
     rendered to each individual patient over time, and such case identifier
     shall be included in the data provided to Amgen. The key or list matching
     patient identities to their unique case identifiers shall not be provided
     to Amgen personnel. In furtherance of Amgen research, Dialysis Center may
     agree from time to time, on terms to be negotiated separately by the
     parties, to use its key to update the patient care data by linking it with
     information concerning health outcomes, quality of life, and other
     pertinent data that may become available to Amgen from other sources. Any
     such linking of data sources shall not provide the identity of any patient
     to Amgen. Amgen agrees that it will maintain data supplied under this
     agreement in confidence and that it will not use such data to identify or
     contact any patient, [DELETED]. No reports by Amgen concerning analyses of
     the data or the results of such research shall disclose the identity of any
     patient. Nothing in this Agreement shall limit Dialysis Center's use of its
     own patient case data, including, without limitation, any and all data to
     be supplied to Amgen hereunder.

11.  Breach of Agreement. Either party may terminate this Agreement for a
     material breach upon 30 days advance written notice specifying the breach,
     provided that such breach remains uncured at the end of the 30 day period,
     [DELETED]. In addition, in the event that Dialysis Center materially
     breaches any provision of this Agreement, and such breach remains uncured
     for 30 days following notice by Amgen specifying the breach, [DELETED],
     Amgen shall have no obligation to continue to offer the terms described
     herein or pay any further discounts or incentives to Dialysis Center,
     except those discounts and/or incentives earned by Dialysis Center up to
     the time of a breach which results in termination.

12.  Governing Law. This Agreement shall be governed by the laws of the State of
     California and the parties submit to the jurisdiction of the California
     courts, both state and federal.

                                      -3-
<PAGE>

                              Amendment #2 to Agreement No. 19990110 (Continued)
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13.  Warranties. Each party represents and warrants to the other that this
     Agreement (a) has been duly authorized, executed, and delivered by it, (b)
     constitutes a valid, legal, and binding agreement enforceable against it in
     accordance with the terms contained herein, and (c) does not conflict with
     or violate any of its other contractual obligations, expressed or implied,
     to which it is a party or by which it may be bound. The party executing
     this Agreement on behalf of Dialysis Center specifically warrants and
     represents to Amgen that it is authorized to execute this Agreement on
     behalf of and has the power to bind Dialysis Center and the Affiliates to
     the terms set forth in this Agreement. [DELETED].

14.  Notices. Any notice or other communication required or permitted hereunder
     (excluding purchase orders) shall be in writing and shall be deemed given
     or made three days after deposit in the United States mails, with proper
     postage for first-class registered or certified mail prepaid, return
     receipt requested, or when delivered personally, or one day following
     traceable delivery to a nationally recognized overnight delivery service
     with instructions for overnight delivery, in each case addressed to the
     parties as follows (or at such other addresses as the parties may notify
     each other of in writing): Dialysis Center: Total Renal Care, Inc., 21250
     Hawthorne Boulevard, Suite 800, Torrance, CA 90503-5517, Attn: Chief
     Financial Officer, with a copy to General Counsel. Amgen, Inc.: One Amgen
     Center Drive, Thousand Oaks, CA 91320-1789, Attn: [DELETED].

15.  Compliance with Health Care Pricing Legislation and Statutes.
     Notwithstanding anything contained herein to the contrary, in order to
     assure compliance, as determined by Amgen in its sole discretion, with any
     existing federal, state or local statute, regulation or ordinance, or at
     any time following the enactment of any federal, state, or local law or
     regulation that in any manner reforms, modifies, alters, restricts, or
     otherwise affects the pricing of or reimbursement available for EPOGEN(R),
     Amgen may, in its sole discretion, upon 30 days notice, [DELETED] or
     exclude any Affiliates from participating in this Agreement unless such
     Affiliate(s) certifies in writing that they are, or will be, exempt from
     the provisions thereunder. If such affected Affiliate(s) does not so
     certify and is therefore excluded from participating in this Agreement,
     Dialysis Center and Amgen shall meet and in good faith [DELETED].

16.  Force Majeure. Neither party will be liable for delays in performance or
     nonperformance of this Agreement or any covenant contained herein if such
     delay or nonperformance is a result of Acts of God, civil or military
     authority, civil disobedience, epidemics, war, failure of carriers to
     furnish transportation, strike, lockout or other labor disturbances,
     inability to obtain material or equipment, or any other cause of like or
     different nature beyond the control of such party.

17.  Miscellaneous. No modification of this Agreement will be effective unless
     made in writing and executed by a duly authorized representative of each
     party, except as otherwise provided hereunder. Neither party may assign
     this Agreement to a third party without the prior written consent of the
     other party, which consent may not be unreasonably withheld, conditioned,
     or delayed. This Agreement may be executed in one or more counterparts,
     each of which is deemed to be an original but all of which taken together
     constitutes one and the same agreement. Whenever a party is permitted by
     this Agreement to act in its discretion, that party shall be required to
     exercise its discretion in good faith and in a reasonable manner. To the
     extent that any provisions of Amgen's general or customary policies and
     procedures or any terms of any purchase order conflict with or are in
     addition to the terms of this Agreement, the terms of this Agreement shall
     govern. Upon expiration or early termination of this Agreement, the rights
     and obligations set forth in sections 8, 13, 19, and 20 shall survive.

                                      -4-
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                              Amendment #2 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

18.  Entire Agreement. This Agreement, together with all of the Appendices
     attached hereto, constitutes the entire understanding between the parties
     and supersedes all prior written or oral proposals, agreements, or
     commitments pertaining to the subject matter herein.

19.  [DELETED].

20.  [DELETED].

     Please retain one fully executed original for your records and return the
     other fully executed original to Amgen.

     The parties executed this Amendment as of the dates set forth below.

     Amgen Inc.                          Total Renal Care, Inc.

     Signature:   /s/ [DELETED]          Signature:   /s/ Richard Whitney
                  ------------------                  -----------------------

     Print Name:  [DELETED]              Print Name:  Richard Whitney
                  -------------------                 -----------------------

     Print Title: [DELETED]              Print Title: CFO
                  -------------------                 -----------------------

     Date:        6/22/00                Date:        6/23/00
                  -------------------                 -----------------------

                                      -5-
<PAGE>

                              Amendment #2 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

                Appendix A: Discount Pricing, Schedule, and Terms
                -------------------------------------------------

1.   Pricing. Dialysis Center may purchase EPOGEN(R) through Authorized
     Wholesalers at a [DELETED]. Amgen reserves the right to change the
     [DELETED] at any time. [DELETED]. Resulting prices do not include any
     wholesaler markup, service fees, or other charges. [DELETED]. Prices
     referenced below are the prices in effect at the time of the Commencement
     Date of this Agreement.

                                   [DELETED]

2.   [DELETED] Incentive. Dialysis Center may qualify for an [DELETED] Incentive
     [DELETED] provided the following requirements are met.

a.   Requirements: Dialysis Center's aggregate Qualified Purchases of EPOGEN(R)
     for [DELETED], by all Affiliates listed on Appendix B on the Commencement
     Date of this Agreement [DELETED], must equal or exceed [DELETED]. In
     addition, at least [DELETED] taken on an overall basis (and not separately
     for each Affiliate) must have [DELETED] (as defined in Section 2(b) below)
     greater than or equal to [DELETED]. If either of these criteria is not met
     during [DELETED], Dialysis Center will not qualify for the [DELETED].

                                      -6-
<PAGE>

                              Amendment #2 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

         Appendix A: Discount Pricing, Schedule, and Terms (continued)
         -------------------------------------------------------------

     In order to participate in the [DELETED], Dialysis Center must provide the
     following items to Amgen or to a data collection vendor specified
     [DELETED], and no later than [DELETED] after [DELETED]. In those cases in
     which Amgen directs Dialysis Center to submit the [DELETED], Dialysis
     Center shall be deemed [DELETED] so long as it does so [DELETED],
     regardless of the [DELETED] to Amgen: [DELETED], (collectively the "Data");
     provided, however, that Dialysis Center shall be [DELETED]. Amgen may
     utilize the Data for any legal purpose, and reserves the right to audit all
     Data, provided that any audit shall not permit access to information
     disclosing the identity of any patient. Under no circumstances should the
     Data include any patient identifiable information including, without
     limitation, name, complete social security number, address or birth date.
     The identity of the account submitting the Data and any association with
     the Data will remain confidential. The [DELETED] test results must be
     derived from [DELETED] taken immediately before dialysis treatment using
     [DELETED] testing method [DELETED], must be reported to the [DELETED], and
     must be submitted [DELETED] in a format acceptable to Amgen. Hand written
     reports are not acceptable; electronic submission of the Data is preferred.

     In addition, upon execution of this Agreement, Dialysis Center shall
     simultaneously provide to Amgen an executed "Annual Certification Letter",
     a copy of which is attached hereto as Exhibit #1. Amgen hereby acknowledges
     that it has received such required Annual Certification Letter, in form and
     substance satisfactory to Amgen. Delivery of such Annual Certification
     Letter shall serve to qualify Dialysis Center's participation in the
     [DELETED] throughout the Term of this Agreement for the limited purpose of
     certification of the accuracy of the data submitted to Amgen hereunder.

b.   Calculation: Assuming Dialysis Center has fulfilled all requirements as
     described in Section 2(a) above, the [DELETED] for Dialysis Center will be
     calculated as follows:

     The [DELETED] for each dialysis patient will be based upon the average of
     all [DELETED] gathered for each patient [DELETED]. The [DELETED] of all
     dialysis patients with [DELETED] greater than or equal to [DELETED], will
     be determined by dividing the total number of dialysis patients with
     [DELETED] greater than or equal to [DELETED], by the total number of
     dialysis patients treated by Dialysis Center during that [DELETED].

c.   Payment: The [DELETED] will be calculated [DELETED] and paid to Dialysis
     Center's corporate headquarters, within [DELETED] after receipt by Amgen of
     all required data. For purposes of calculating the [DELETED] as referenced
     in Section 2 a) above, Amgen will compare the [DELETED] by all Affiliates
     listed on Appendix B on the Commencement Date of this Agreement [DELETED],
     to the aggregate Qualified Purchases of EPOGEN(R) by those same Affiliates
     listed on Appendix B on the Commencement Date of this Agreement [DELETED].

                                      -7-
<PAGE>

                              Amendment #2 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

         Appendix A: Discount Pricing, Schedule, and Terms (continued)
         -------------------------------------------------------------

     [DELETED]. At any time during the Term of this Agreement, if Amgen
     determines that any Affiliate(s) is consistently not submitting the
     required Data, Amgen reserves the right in its sole discretion to exclude
     such Affiliate's Qualified Purchases of EPOGEN(R) from the calculation of
     the [DELETED]. [DELETED] payments will be based upon the Data received
     [DELETED], and will equal a percentage of Dialysis Center's total Qualified
     Purchases of EPOGEN(R) [DELETED] (exclusive of any Qualified Purchases of
     EPOGEN(R) made by Dialysis Center or any Affiliate not meeting the Data
     submission requirements described above) as governed by the [DELETED]
     schedule listed below. [DELETED]. Amgen reserves the right to modify the
     [DELETED] if the EPOGEN(R) package insert language changes. [DELETED].

<TABLE>
     <S>                                                               <C>
            [DELETED] of all dialysis patients                              [DELETED]
     with [DELETED] greater than or equal to [DELETED]                 Incentive Percentage
     Please direct your attention to the EPOGEN(R) package insert      --------------------
     ------------------------------------------------------------
</TABLE>
                                   [DELETED]

     [DELETED].

d.   Vesting:  Dialysis Center's [DELETED] will vest on [DELETED].

                                      -8-
<PAGE>

                              Amendment #2 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

          Appendix A: Discount Pricing, Schedule, and Terms (continued)
          -------------------------------------------------------------

e.   [DELETED] Conversion: Dialysis Center may choose to submit [DELETED] test
     results rather than [DELETED] test results as a measurement of [DELETED].
     If during the Term, Dialysis Center elects to use [DELETED] test results,
     Dialysis Center must: i) submit a "Notification Letter" to Amgen, a sample
     of such Notification Letter is attached hereto as Exhibit #2, and ii) begin
     submitting all [DELETED] test results for all dialysis patients along with
     all other information described in Section 2(a) above, rather than
     [DELETED] test results for all dialysis patients at each Affiliate for
     purposes of participating in the [DELETED]. Amgen will accept the [DELETED]
     test results, [DELETED], and apply the converted results to the same
     schedule, requirements, and calculations described above in place of the
     [DELETED] test results. For the [DELETED] in which Dialysis Center submits
     its Notification Letter ("Grace Period"), Amgen will apply Dialysis
     Center's [DELETED] in which complete [DELETED] test results were received
     [DELETED] to the [DELETED] schedule listed above in order to determine the
     applicable [DELETED] Percentage earned by Dialysis Center. If Dialysis
     Center's overall performance on the [DELETED] after the Grace Period does
     not equal or exceed the overall performance by Dialysis Center prior to
     [DELETED], Amgen will continue to apply Dialysis Center's [DELETED] through
     the remainder of the Term, provided that during the time period the
     [DELETED] is so applied, Dialysis Center's aggregate EPOGEN(R)purchases by
     all Affiliates listed on Appendix B on the Commencement Date of this
     Agreement [DELETED], equals or exceeds [DELETED] by those same Affiliates
     listed on Appendix B on the Commencement Date of this Agreement [DELETED],
     for the same time period from the previous year. In the event any
     Affiliates still submitting Data based on [DELETED] test results are added
     to this Agreement after Dialysis Center has converted to [DELETED], such
     [DELETED], for [DELETED] in which they were added, shall be included in the
     calculation of the [DELETED] payment. In order for such added Affiliates'
     Qualified Purchases of EPOGEN(R)to be included in all subsequent [DELETED]
     payment calculations, such Affiliate must submit [DELETED] test results
     rather than [DELETED].

3.   [DELETED]. Dialysis Center shall be eligible to receive a [DELETED] if
     certain data elements are transmitted to Amgen [DELETED]. The [DELETED]
     will be calculated as a percentage of the Qualified Purchases of
     EPOGEN(R)attributable to Dialysis Center during [DELETED]. [DELETED]. In
     order to qualify for the [DELETED], the following [DELETED] must be
     submitted to Amgen by all Affiliates in [DELETED] acceptable to Amgen
     [DELETED] Facility ID, [DELETED]. Such [DELETED] must be submitted, on a
     [DELETED], and no later than [DELETED].[DELETED]. However, if Amgen
     reasonably determines that any Affiliate is consistently not submitting the
     required data, Amgen reserves the right in its sole discretion to exclude
     such Affiliate's Qualified Purchases of EPOGEN(R)from the calculation of
     the [DELETED] for [DELETED]. The [DELETED] will vest on [DELETED], and
     payments will be made [DELETED], contingent upon receipt by Amgen of all
     [DELETED]. [DELETED]

                                      -9-
<PAGE>

                              Amendment #2 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

          Appendix A: Discount Pricing, Schedule, and Terms (continued)
          -------------------------------------------------------------

     [DELETED].

4.   [DELETED]. Dialysis Center may qualify for the [DELETED] as described
     below.

a.   Calculation: Dialysis Center's [DELETED] will be calculated [DELETED] in
     accordance with the following formula.

                                   [DELETED]

[DELETED].

For purposes of calculating the [DELETED], Amgen will incorporate Qualified
Purchases of EPOGEN(R) from [DELETED].

[DELETED].

[DELETED] payments will be made within [DELETED], contingent upon receipt by
Amgen of all necessary [DELETED]. [DELETED].

                                      -10-
<PAGE>

                              Amendment #2 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

         Appendix A: Discount Pricing, Schedule, and Terms (continued)
         -------------------------------------------------------------

[DELETED].

b.   Vesting: Dialysis Center's [DELETED] will vest [DELETED], and will be paid
     in accordance with the terms and conditions described above.

                                      -11-
<PAGE>

                              Amendment #2 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

                Appendix B: List of Dialysis Center Affiliates

                               (See Referenced)

To ensure you receive the appropriate discount, it is important that we have
your current list of Authorized Wholesalers. The following list represents the
Wholesalers Amgen currently has associated with your contract. Please update the
list by adding or deleting Wholesalers as necessary.

[DELETED]

                                      -12-
<PAGE>

                              Amendment #2 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

                                                                      Exhibit #1
                         Annual Certification Letter
                         ---------------------------

June 21, 2000

Total Renal Care, Inc.
21250 Hawthorne Boulevard, Suite 800
Torrance, CA  90503

RE:  EPOGEN(R) (Epoetin alfa) Agreement No. 19990110

Dear [DELETED]:

Thank you for your participation in the [DELETED]. In order for us to process
your data, we require that a duly authorized representative of your organization
sign the certification below.

Upon receipt of this executed document, we will calculate the value of your
incentive. If we do not receive the executed certification, we cannot provide
you with this incentive.

If you have any questions regarding this letter please contact me at [DELETED].
Thank you for your assistance in returning this certification.

Sincerely,

[DELETED]
[DELETED] Incentive Analyst

CERTIFICATION:

On behalf of Total Renal Care, Inc. and all eligible Affiliates participating in
the [DELETED] under Agreement No. 19990110, the undersigned hereby certifies
that the [DELETED] and any other data required to be submitted (herein referred
to as "Data"), for each eligible Affiliate during the term of this Agreement
shall include the required Data from all dialysis patients from each such
Affiliate, [DELETED]. The party executing this document also represents and
warrants that it (i) has no reason to believe that the submitted Data will be
incorrect, and (ii) is authorized to make this certification on behalf of all
eligible Affiliates submitting Data.

Total Renal Care, Inc.

Signature:     /s/ [DELETED]
               -------------------------------
Print Name:    [DELETED]
               -------------------------------
Print Title:   Director, Purchasing
               -------------------------------
Date:          6/23/2000
               -------------------------------

                                      -13-
<PAGE>

                              Amendment #2 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

                                                                      Exhibit #2

                          Sample Notification Letter
                          --------------------------

Month X, 2000

[DELETED]
[DELETED] Incentive Analyst
Amgen Inc. [DELETED]
One Amgen Center Drive [DELETED]
Thousand Oaks, CA  91320

RE:  Amgen Agreement No. XXXXXX

Dear [DELETED]:

This letter serves as notification that FSDC Legal Name and all eligible
Affiliates participating in the [DELETED] under Agreement No. XXXXXX, will begin
using [DELETED] test results as a measurement of [DELETED] as of Month X, 199X,
and will begin submitting [DELETED] test results rather than [DELETED] test
results for purposes of participating in the [DELETED].

We understand that any discount under the [DELETED] will now be based solely on
[DELETED] test results and that [DELETED] test results will no longer be
accepted. We also understand that such [DELETED] test results will be [DELETED]
and applied to the same schedule, requirements, and calculations described in
the [DELETED] outlined in the Agreement.

Sincerely,

Name of Administrator
Title

                                      -14-
<PAGE>

                                                                 [LOGO OF AMGEN]
                                                 One Amgen Center Drive
                                                 Thousand Oaks, CA 91320-1799
January 17, 2001

Total Renal Care, Inc.
Attn:  Rich Whitney
21250 Hawthorne Boulevard, Suite 800
Torrance, CA  90503

Re: EPOGEN/(R)/ Purchase Agreement #19990110, as amended; [DELETED].

Dear Rich Whitney:

Reference is made to the Agreement indicated above (the "Agreement") by and
between Amgen Inc. ("Amgen") and Total Renal Care, Inc. ("TRC") for the purchase
of EPOGEN/(R)/.

[DELETED].

Please note that this letter shall be considered a modification to the Agreement
and as such should be signed by both parties. Except as herein modified, all
other terms of the Agreement shall remain in full force and effect. Please
confirm that you are duly authorized to sign and commit on behalf of TRC
hereunder and that you have read, understand and agree to the terms of this
letter by signing below and returning the signed original copy of the letter to
me at the address provided above on the letterhead. A copy of this letter is
enclosed for your records.

If you have any questions or comments, please feel free to contact me at
805-313-7480. We look forward to receiving a signed copy of this letter and are
anxious to develop our ongoing relationship for the benefit of patients
undergoing dialysis.

Sincerely,
   /s/
[DELETED]
National Account Manager

ACKNOWLEDGED AND AGREED:

Date:  January ____, 2001

Total Renal Care, Inc.

By:    /s/ Richard K. Whitney
       ----------------------------

Name:  Richard K. Whitney
       ----------------------------

Title: CFO
       ----------------------------<PAGE>

                                                                   EXHIBIT 10.25
AMGEN

                   Amendment #3 dated January 16, 2001 to Agreement No. 19990110
--------------------------------------------------------------------------------

Agreement No. 19990110, between Amgen Inc. ("Amgen") and Total Renal Care, Inc.,
a subsidiary of DaVita, Inc., including any prior amendments thereto, shall be
amended, and for the period commencing April 1, 2001 shall be restated in its
entirety to read in full as stated below.

This agreement ("Agreement") together with all Appendices attached hereto and
incorporated herein by this reference, between Amgen and Total Renal Care, Inc.
including the freestanding dialysis center affiliate(s) listed on Appendix B,
(collectively, "Dialysis Center"), sets forth the terms and conditions for the
purchase of EPOGEN(R) (Epoetin alfa) by Dialysis Center for the exclusive
treatment of dialysis patients.

1.   Term of Agreement. The "Term" of this Agreement shall be defined as April
     1, 2001 ("Commencement Date") through December 31, 2001 ("Termination
     Date").

2.   Dialysis Center Affiliates. Dialysis Center must provide Amgen with a
     complete list of its dialysis center affiliates ("Affiliates") no less than
     fifteen (15) business days before the Commencement Date. Affiliates
     eligible to participate under this Agreement shall be listed in Appendix B,
     and shall reflect facilities owned in whole or in part by Dialysis Center
     or for which Dialysis Center provides management or administrative
     services, such services to include the purchase and billing of EPOGEN(R).
     Additions to the dialysis center Affiliates listed on Appendix B may be
     made pursuant to the request of Dialysis Center's corporate headquarters
     and are subject to approval and acknowledgment by Amgen in writing, such
     approval and acknowledgment not to be unreasonably withheld, conditioned or
     delayed. Dialysis Center may delete Affiliates from participation in this
     Agreement at any time, in its sole discretion. Amgen requires reasonable
     notice before the effective date of change (the "Administrative Effective
     Date") for any addition or deletion of Affiliates. [DELETED]; all such
     purchases by Dialysis Center during such period shall constitute "Qualified
     Purchases" under this Agreement and shall be included for purposes of
     eligibility and calculation of each and every discount and incentive
     provided hereunder and in Appendix A, including but not limited to,
     [DELETED] set forth in Section 1 of Appendix A, so long as Amgen is not
     obligated to pay the same discount or incentive attributable to the same
     purchases to any person or entity other than Dialysis Center. Amgen
     reserves the right in its reasonable discretion to terminate any Affiliates
     with regard to participation in this Agreement. Termination of any
     Affiliate by Amgen shall be effective (a) immediately in instances in which
     Amgen determines, in its discretion, that such immediate termination is
     required by law or order of any court or regulatory agency or as a result
     of negligence in the use or administration of EPOGEN(R) by such Affiliate;
     or (b) upon 30 days prior written notice to Dialysis Center in all other
     instances; provided, that such termination shall be effective before the
     expiration of such 30 days where Dialysis Center requests or consents to
     such earlier termination.

3.   Own Use. Dialysis Center hereby certifies that EPOGEN(R)purchased hereunder
     shall be for Dialysis Center's "own use", for the exclusive treatment of
     dialysis patients.

4.   Authorized Wholesalers. Dialysis Center must provide Amgen with a complete
     list of its current wholesalers, from whom Dialysis Center intends to
     purchase EPOGEN(R), and must provide the list to Amgen no less than fifteen
     (15) business days before the Commencement Date. The list must include the
     name and complete address of each designated wholesaler. Wholesalers
     designated by Dialysis Center and approved by Amgen to participate in this
     program will be deemed "Authorized Wholesalers". A current listing of
     Dialysis Center's Authorized Wholesalers is referenced in Appendix C.
     Notification of proposed changes to the list of Authorized Wholesalers must
     be provided to Amgen in writing at least 30 days before the effective date
     of the proposed change; provided, however, that Amgen will use its best
     efforts to accept a change in fewer than 30 days' notice. Amgen reserves
     the right, in its reasonable discretion, to reject or terminate, with
     reasonable notice, any wholesaler with regard to participation in this
     Agreement, so long as (a) Amgen rejects or terminates such wholesaler with
     respect to providing EPOGEN(R) to any and all purchasers of EPOGEN(R), or
     (b) such wholesaler independently requests Amgen to remove it as an
     Authorized Wholesaler for Dialysis Center. Amgen also reserves the right,
     in its reasonable discretion, to accept wholesalers with regards to
     participation in this Agreement, but Amgen agrees that it shall accept any
     Wholesaler designated by Dialysis Center which provides EPOGEN(R) to other
     purchasers approved by Amgen. Dialysis Center agrees to request all
     Authorized Wholesalers to submit product sales information to a third-party
     sales reporting organization designated by Amgen. In the event Amgen
     terminates any Authorized Wholesaler from which Dialysis Center is
     purchasing EPOGEN(R), Amgen will work with Dialysis Center to identify
     other possible Authorized Wholesalers from which Dialysis Center may
     purchase EPOGEN(R) [DELETED].

                                      -1-
<PAGE>

                              Amendment #3 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

5.   Qualified Purchases. Only EPOGEN(R)purchased under this Agreement by
     Dialysis Center through Authorized Wholesalers [DELETED], as confirmed by
     Amgen based on sales tracking data, will be deemed "Qualified Purchases".

6.   Commitment to Purchase. Dialysis Center agrees to purchase EPOGEN(R) for
     all of its dialysis use requirements for recombinant human erythropoietin,
     and Amgen agrees to supply through Authorized Wholesalers all orders as
     placed by Dialysis Center. Notwithstanding the foregoing, Amgen expressly
     acknowledges and agrees that Dialysis Center may participate in clinical
     trials involving the administration of other products for the management of
     anemia in dialysis patients. Dialysis Center may purchase another brand of
     recombinant human erythropoietin for its dialysis use requirements only for
     the time, and only to the extent, that Amgen has notified Dialysis Center's
     corporate headquarters in writing that Amgen cannot supply EPOGEN(R) within
     and for the time period reasonably required by Dialysis Center. Any such
     notification shall be given by Amgen at least 30 days prior to the date on
     which Amgen will cease supplying EPOGEN(R) to Dialysis Center, unless an
     act or event described in Section 16 below, or an order of a regulatory
     agency or other action arising out of patient safety concerns, requires the
     giving of shorter notice. In the event that Amgen fails to supply Dialysis
     Center with EPOGEN(R) as ordered, Dialysis Center shall be entitled, at a
     minimum, to have the same proportion of its purchase orders fulfilled at
     all times as other purchasers of EPOGEN(R) and, upon request, Amgen shall
     provide written assurances of same to Dialysis Center.

7.   Confidentiality. Both Amgen and Dialysis Center agree that this Agreement
     represents and contains confidential information which shall not be
     disclosed to any third party, or otherwise made public, without prior
     written authorization of the other party, except where such disclosure is
     contemplated hereunder or required by law or pursuant to subpoena or court
     or administrative order, and then only upon prior written notification to
     the other party giving such party an adequate opportunity to take whatever
     steps it deems necessary to prevent, limit the scope of or contest the
     disclosure. [DELETED].

8.   Discounts. Dialysis Center shall qualify for discounts and incentives
     subject to material compliance with the terms and conditions of this
     Agreement as well as the schedules and terms set forth in Appendix A, which
     is incorporated by reference hereto and made a part of this Agreement.
     Discounts in arrears will be paid [DELETED] to Dialysis Center's corporate
     headquarters. Discounts in arrears will be calculated in accordance with
     Amgen's discount calculation policies based on Qualified Purchases using
     the [DELETED] as the calculation price, except as otherwise provided
     hereunder or as set forth in Appendix A. Upon vesting, Amgen will make such
     discounts available [DELETED], after receipt by Amgen of all required data,
     in a form reasonably acceptable to Amgen, detailing all Qualified Purchases
     during the applicable period. Payment amounts, as calculated by Amgen, must
     equal or exceed $100.00 for the applicable period to qualify, and are
     subject to audit and final determination [DELETED], as provided in Appendix
     A hereto. Subject to the section entitled "Breach of Agreement", in the
     event that Amgen is notified in writing that Dialysis Center, and/or any
     Affiliate(s) (the "Acquired Party") is acquired by another entity or a
     change of control otherwise occurs with respect to any Acquired Party, any
     discounts which may have been earned hereunder for all periods preceding
     such acquisition or change of control shall be paid in the form of a wire
     transfer to Dialysis Center's corporate headquarters, subject to the
     conditions and requirements described herein. [DELETED]. Amgen and Dialysis
     Center agree that, for purposes of determining eligibility for and
     calculation of all discounts and all incentives provided in this Agreement
     (including, without limitation, all discounts and incentives as are set
     forth in Appendix A), a Qualified Purchase of EPOGEN(R) shall be deemed
     made on the date of invoice to Dialysis Center from an Authorized
     Wholesaler. Upon any termination of this Agreement, Amgen shall pay to
     Dialysis Center all discounts and incentives earned by Dialysis Center
     through the date of termination. Failure of Dialysis Center to qualify for
     or receive any particular discount or incentive hereunder shall not
     automatically affect its qualification for or receipt of any other discount
     or incentive provided under this Agreement.

9.   Treatment of Discounts. [DELETED] Dialysis Center agrees that it will
     properly disclose and account for any discount or other reduction in price
     earned hereunder, in whatever form(i.e. pricing, discount, or incentive),
     in a way that complies with all applicable federal, state, and local laws
     and regulations, including without limitation, Section 1128B(b) of the
     Social Security Act and its implementing regulations. Section 1128B(b)
     requires that a provider of services will properly disclose and
     appropriately reflect the value of any discount or other reduction in price
     earned in the costs claimed or charges made by the provider under a federal
     health care program, as that term is defined in Section 1128B(f). Dialysis
     Center also agrees that, if required by such statutes or regulations, it
     will (i) claim the benefit of such discount received, in whatever form, in
     the fiscal year in which such discount was earned or the year after, (ii)
     fully and accurately report the value of such discount in any cost reports
     filed under Title XVIII or Title XIX of the Social Security Act, or a state
     health

                                      -2-
<PAGE>

                   Amendment #3 dated January 16, 2001 to Agreement No. 19990110
--------------------------------------------------------------------------------

     care program, and (iii) provide, upon request by the U.S. Department of
     Health and Human Services or a state agency or any other federally funded
     state health care program, the information furnished to Dialysis Center by
     Amgen concerning the amount or value of such discount. Dialysis Center's
     corporate headquarters agrees that it will advise all Affiliates, in
     writing, of any discount received by Dialysis Center's corporate
     headquarters hereunder with respect to purchases made by such Affiliates
     and that said Affiliates will account for any such discount in accordance
     with the above stated requirements.

     [DELETED].

10.  Data Collection. Dialysis Center agrees that it will at all times comply
     with all federal, state, or local laws or regulations relating to patient
     privacy of medical records, and that all data to be provided to Amgen
     pursuant to this Agreement, shall be in a form that does not disclose the
     identity or name of any patient or other patient-identifying information
     such as address, telephone number, or social security number. Dialysis
     Center acknowledges that the data to be supplied to Amgen pursuant to this
     Agreement shall be used to support verification of the discounts and
     incentives referenced herein, as well as for Amgen-sponsored research
     concerning the role of EPOGEN(R) in improving treatment outcomes and
     quality of life of dialysis patients. Dialysis Center shall consistently
     use a unique alpha-numeric code (which shall not be the same as the
     patient's social security number) as a "case identifier" to track the care
     rendered to each individual patient over time, and such case identifier
     shall be included in the data provided to Amgen. The key or list matching
     patient identities to their unique case identifiers shall not be provided
     to Amgen personnel. In furtherance of Amgen research, Dialysis Center may
     agree from time to time, on terms to be negotiated separately by the
     parties, to use its key to update the patient care data by linking it with
     information concerning health outcomes, quality of life, and other
     pertinent data that may become available to Amgen from other sources. Any
     such linking of data sources shall not provide the identity of any patient
     to Amgen. Amgen agrees that it will maintain data supplied under this
     Agreement in confidence and that it will not use such data to identify or
     contact any patient, and that it will at all times comply with all federal,
     state, or local laws or regulations relating to patient records. [DELETED].
     No reports by Amgen concerning analyses of the data or the results of such
     research shall disclose the identity of any patient. Nothing in this
     Agreement shall limit Dialysis Center's use of its own patient case data,
     including, without limitation, any and all data to be supplied to Amgen
     hereunder.

11.  Breach of Agreement. in addition to any other legal or equitable remedies
     which may be available to either party upon breach by the other party, such
     party may terminate this Agreement for a material breach upon 30 days
     advance written notice specifying the breach, provided that such breach
     remains uncured at the end of the 30 day period, [DELETED]. In addition, in
     the event that Dialysis Center materially breaches any provision of this
     Agreement, and such breach remains uncured for 30 days following notice by
     Amgen specifying the breach, [DELETED], Amgen shall have no obligation to
     continue to offer the terms described herein or pay any further discounts
     or incentives to Dialysis Center, except those discounts and/or incentives
     earned by Dialysis Center up to the time of a breach which results in
     termination.

12.  Governing Law. This Agreement shall be governed by the laws of the State of
     California and, [DELETED], the parties submit to the jurisdiction of the
     California courts, both state and federal.

13.  Warranties. Each party represents and warrants to the other that this
     Agreement (a) has been duly authorized, executed, and delivered by it, (b)
     constitutes a valid, legal, and binding agreement enforceable against it in
     accordance with the terms contained herein, and (c) does not conflict with
     or violate any of its other contractual obligations, expressed or implied,
     to which it is a party or by which it may be bound. The party executing
     this Agreement on behalf of Dialysis Center specifically warrants and
     represents to Amgen that it is authorized to execute this Agreement on
     behalf of and has the power to bind Dialysis Center and the Affiliates to
     the terms set forth in this Agreement. [DELETED].

14.  Notices. Any notice or other communication required or permitted hereunder
     (excluding purchase orders) shall be in writing and shall be deemed given
     or made three days after deposit in the United States mails, with proper
     postage for first-class registered or certified mail prepaid, return
     receipt requested, or when delivered personally or by facsimile, or one day
     following traceable delivery to a nationally recognized overnight delivery
     service with instructions for overnight delivery, in each case addressed to
     the parties as follows (or at such other addresses as the parties may
     notify each other of in writing):

                                      -3-
<PAGE>

                   Amendment #3 dated January 16, 2001 to Agreement No. 19990110
--------------------------------------------------------------------------------

          If to Dialysis Center:
                                 Total Renal Care, Inc.
                                 21250 Hawthorne Boulevard, Suite 800
                                 Torrance, CA  90503-5517
                                 Attn:  Chief Financial Officer
                                 Fax No.:  [DELETED]

                  with a copy to:
                                 Total Renal Care, Inc.
                                 21250 Hawthorne Boulevard, Suite 800
                                 Torrance, CA  90503-5517
                                 Attn:  General Counsel
                                 Fax No.:  [DELETED]

          If to Amgen:
                                 Amgen Inc.
                                 One Amgen Center Drive, M/S 37-2-A
                                 Thousand Oaks, CA  91320-1789
                                 Attn: [DELETED]
                                 Fax No.: [DELETED]

                  with a copy to:
                                 Amgen Inc.
                                 One Amgen Center Drive, M/S 27-4-A
                                 Thousand Oaks, CA  91320-1789
                                 Attn:  [DELETED]
                                 Fax No.:  [DELETED]

15.  Compliance with Health Care Pricing and Patient Privacy Legislation and
     Statutes. a) Notwithstanding anything contained herein to the contrary, in
     order to assure compliance, as determined by Amgen in its sole discretion,
     with any existing federal, state or local statute, regulation or ordinance,
     or at any time following the enactment of any federal, state, or local law
     or regulation that in any manner reforms, modifies, alters, restricts, or
     otherwise affects the pricing of or reimbursement available for EPOGEN(R),
     Amgen may, in its sole discretion, upon 30 days notice, [DELETED] exclude
     any Affiliates from participating in this Agreement unless such
     Affiliate(s) certifies in writing that they are, or will be, exempt from
     the provisions thereunder. If such affected Affiliate(s) does not so
     certify and is therefore excluded from participating in this Agreement,
     Dialysis Center and Amgen shall meet and in good faith [DELETED].

     b) Notwithstanding anything contained herein to the contrary, in order to
     assure compliance, as determined by either party in its sole discretion,
     with any existing federal, state or local statute, regulation or ordinance
     relating to patient privacy of medical records, or at any time following
     the enactment of any federal, state, or local law or regulation relating to
     patient privacy of medical records that in any manner reforms, modifies,
     alters, restricts, or otherwise affects any of the data received or to be
     received in connection with any of the incentives contemplated under this
     Agreement, either party may, in its discretion, upon 30 days' notice, seek
     to modify this Agreement. Dialysis Center and Amgen shall meet and in good
     faith seek to mutually agree to modify this Agreement to accommodate any
     such change in law or regulation, [DELETED]. If the parties in good faith
     determine that such modification is not possible, the parties shall seek to
     modify the Agreement in another manner acceptable to both parties. If the
     parties, after a reasonable time, are unable to agree upon such a
     modification, Amgen shall be entitled to terminate the affected incentive
     upon 30 days' notice.

16.  Force Majeure. Neither party will be liable for delays in performance or
     nonperformance of this Agreement or any covenant contained herein if such
     delay or nonperformance is a result of Acts of God, civil or military
     authority, civil disobedience, epidemics, war, failure of carriers to
     furnish transportation, strike, lockout or other labor disturbances,
     inability to obtain material or equipment, or any other cause of like or
     different nature beyond the control of such party.

                                      -4-
<PAGE>

                   Amendment #3 dated January 16, 2001 to Agreement No. 19990110
--------------------------------------------------------------------------------

17.  Miscellaneous. No modification of this Agreement will be effective unless
     made in writing and executed by a duly authorized representative of each
     party, except as otherwise provided hereunder. Neither party may assign
     this Agreement to a third party without the prior written consent of the
     other party, which consent may not be unreasonably withheld, conditioned,
     or delayed. This Agreement may be executed in one or more counterparts,
     each of which is deemed to be an original but all of which taken together
     constitutes one and the same agreement. Whenever a party is permitted by
     this Agreement to act in its discretion, that party shall be required to
     exercise its discretion in good faith and in a reasonable manner. To the
     extent that any provisions of Amgen's general or customary policies and
     procedures or any terms of any purchase order conflict with or are in
     addition to the terms of this Agreement or any Appendix attached hereto,
     the terms of this Agreement and Appendices shall govern. Upon expiration or
     early termination of this Agreement, the rights and obligations set forth
     in sections 7, 8, 10, 13, 19, and 20 shall survive.

18.  Entire Agreement. This Agreement, together with all of the Appendices
     attached hereto, constitutes the entire understanding between the parties
     and supersedes all prior written or oral proposals, agreements, or
     commitments pertaining to the subject matter herein.

19.  [DELETED].

     [DELETED].

20.  [DELETED].

                                      -5-
<PAGE>

                   Amendment #3 dated January 16, 2001 to Agreement No. 19990110
--------------------------------------------------------------------------------

Please retain one fully executed original for your records and return the other
fully executed original to Amgen.

The parties executed this Amendment as of the dates set forth below.

<TABLE>
<S>                                                <C>
Amgen Inc.                                         Total Renal Care, Inc.

Signature:   /s/ [DELETED]                         Signature: /s/ Richard K. Whitney
            ---------------------------------                  -------------------------
Print Name:  [DELETED]                             Print Name: Richard K. Whitney
            ---------------------------------                  -------------------------
Print Title: [DELETED]                             Print Title:   CFO
            ---------------------------------                  -------------------------
Date:        1/17/2001                             Date:        1/17/01
            ---------------------------------                  -------------------------
</TABLE>

                                      -6-
<PAGE>

                   Amendment #3 dated January 16, 2001 to Agreement No. 19990110
--------------------------------------------------------------------------------

               Appendix A: Discount Pricing, Schedule, and Terms
               -------------------------------------------------

1.   Pricing. Throughout the Term of this Agreement (April 1, 2001 - December
     31, 2001), Dialysis Center may purchase EPOGEN(R) through Authorized
     Wholesalers at [DELETED]. Amgen reserves the right to change the [DELETED]
     at any time, which change [DELETED] Dialysis Center during the Term of this
     Agreement. [DELETED]. Resulting prices do not include any wholesaler
     markup, service fees, or other charges. All discounts earned in arrears
     during the Term of the Agreement shall be calculated based upon the
     [DELETED].

2.   [DELETED]. Dialysis Center may qualify for a [DELETED] provided it meets
     the criteria described below in this section. The [DELETED] is designed to
     improve patient outcomes by encouraging [DELETED].

a.   Requirements: In order to qualify for the [DELETED], Dialysis Center's
     aggregate Qualified Purchases of EPOGEN(R)for [DELETED], by all Affiliates
     listed on Appendix B on the Commencement Date of this Agreement [DELETED],
     must equal or exceed [DELETED]. In addition, [DELETED]. If either of these
     criteria is not met during [DELETED], Dialysis Center will not qualify for
     the [DELETED]. [DELETED].

     In order to participate in the [DELETED], Dialysis Center must provide the
     following items to Amgen or to a data collection vendor specified
     [DELETED], and no later than [DELETED]. In those cases in which Amgen
     directs Dialysis Center to submit [DELETED], Dialysis Center shall be
     deemed [DELETED] so long as it does so [DELETED], regardless of the
     [DELETED] to Amgen: [DELETED]

                                      -7-
<PAGE>

                              Amendment #3 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

         Appendix A: Discount Pricing, Schedule, and Terms (continued)
         -------------------------------------------------------------

    [DELETED]. Amgen may utilize the Data for any legal purpose, and reserves
    the right to audit all Data, provided that any audit shall not permit access
    to information disclosing the identity of any patient. Under no
    circumstances should the Data include any patient identifiable information
    including, without limitation, name, complete social security number,
    address or birth date. The identity of the account submitting the Data and
    any association with the Data will remain confidential. The [DELETED] test
    results must be derived from [DELETED] taken immediately before dialysis
    treatment using any [DELETED] testing method [DELETED] must be reported to
    the [DELETED], and must be submitted [DELETED] in a format acceptable to
    Amgen. Hand written reports are not acceptable; electronic submission of the
    Data is preferred.

    In addition, upon execution of this Agreement, Dialysis Center shall
    simultaneously provide to Amgen an executed "Certification Letter", a copy
    of which is attached hereto as Exhibit #1. Amgen hereby acknowledges that it
    has received such required Certification Letter, in form and substance
    satisfactory to Amgen. Delivery of such Certification Letter shall serve to
    qualify Dialysis Center's participation in the [DELETED] throughout the Term
    of this Agreement for the limited purpose of certification of the accuracy
    of the data submitted to Amgen hereunder.

b.  Calculation: Assuming Dialysis Center has fulfilled all requirements as
    described in Section 2(a) above, the [DELETED] for Dialysis Center will be
    calculated as follows:

    The [DELETED] for each dialysis patient will be based upon the average of
    all [DELETED] gathered for each patient [DELETED]. The [DELETED] of all
    dialysis patients with [DELETED], will be determined by dividing the total
    number of dialysis patients with [DELETED] by the total number of dialysis
    patients treated by Dialysis Center during that [DELETED].

c.  Payment: The [DELETED] will be calculated [DELETED] and paid to Dialysis
    Center's corporate headquarters, within [DELETED] after receipt by Amgen of
    all required data. For purposes of calculating the [DELETED] as referenced
    in Section 2 (a) above, Amgen will compare the aggregate Qualified Purchases
    of EPOGEN(R) [DELETED] by all Affiliates listed on Appendix B on the
    Commencement Date of this Agreement [DELETED], to the aggregate Qualified
    Purchases of EPOGEN(R) by those same Affiliates listed on Appendix B on the
    Commencement Date of this Agreement [DELETED].

    [DELETED]

                                      -8-
<PAGE>

                              Amendment #3 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

         Appendix A: Discount Pricing, Schedule, and Terms (continued)
         -------------------------------------------------------------

    [DELETED]. At any time during the Term of this Agreement, if Amgen
    determines that any Affiliate(s) is consistently not submitting the required
    Data, Amgen reserves the right in its sole discretion to exclude such
    Affiliate's Qualified Purchases of EPOGEN(R) from the calculation of the
    [DELETED]. [DELETED] payments will be made based upon the Data received from
    [DELETED], and will equal [DELETED] Qualified Purchases of EPOGEN(R)
    [DELETED] (exclusive of any Qualified Purchases of EPOGEN(R) made by
    Dialysis Center or any Affiliate not meeting the Data submission
    requirements described above) as governed by the [DELETED] schedule listed
    below. If Amgen determines that any Affiliate is consistently not submitting
    the required Data, Amgen and Dialysis Center will work collaboratively in
    resolving such matters. [DELETED]. If the EPOGEN(R) package insert language
    or the K/DOQI guidelines change, [DELETED].

              [DELETED] of all dialysis patients                 [DELETED]
                        with [DELETED]                      Incentive Percentage
    Please direct your attention to the EPOGEN(R) package
    ----------------------------------------------------------------------------
    insert
    ------

                                          [DELETED]

    [DELETED].

d.  Vesting:  Dialysis Center's [DELETED] Incentive will vest on [DELETED].

                                      -9-
<PAGE>

                              Amendment #3 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

         Appendix A: Discount Pricing, Schedule, and Terms (continued)
         -------------------------------------------------------------

e.  [DELETED] Data Submission: In the event any Affiliates still submitting Data
    based on [DELETED] test results are added to this Agreement, such
    Affiliate's Qualified Purchases of EPOGEN(R), from the day it was added
    through the [DELETED] in which it was added [DELETED], shall be included in
    the calculation of the [DELETED] Incentive payment. [DELETED]. In order for
    such added Affiliates' Qualified Purchases of EPOGEN(R) to be included in
    all subsequent [DELETED] Incentive payment calculations, such Affiliate must
    submit [DELETED].

3.  [DELETED]. Dialysis Center shall be eligible to receive [DELETED] if certain
    data elements are transmitted to Amgen [DELETED]. The [DELETED] will be
    calculated as a percentage of the Qualified Purchases of
    EPOGEN(R)attributable to Dialysis Center [DELETED]. [DELETED]. In order to
    qualify for the [DELETED], the following [DELETED] must be submitted to
    Amgen by all Affiliates [DELETED] acceptable to Amgen [DELETED]. Such
    [DELETED] must be submitted, [DELETED], and no later than [DELETED]. Amgen
    reserves the right in its sole discretion to exclude any consistently non-
    reporting Affiliate's Qualified Purchases of EPOGEN(R)from the calculation
    of the [DELETED]. The [DELETED] will vest [DELETED], and payments will be
    made [DELETED]. The [DELETED]

                                      -10-
<PAGE>

                              Amendment #3 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

         Appendix A: Discount Pricing, Schedule, and Terms (continued)
         -------------------------------------------------------------

[DELETED].

4.  [DELETED].  Dialysis Center may qualify for the [DELETED] as described
    below.

a.  Calculation: Dialysis Center's [DELETED] will be calculated [DELETED] in
    accordance with the following formula.

                                   [DELETED]

For purposes of calculating the [DELETED], Amgen will incorporate Qualified
Purchases of EPOGEN(R) from [DELETED].

[DELETED].

[DELETED] payments will be made [DELETED], contingent upon receipt by Amgen of
all necessary [DELETED]. [DELETED]

                                      -11-
<PAGE>

                              Amendment #3 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

         Appendix A: Discount Pricing, Schedule, and Terms (continued)
         -------------------------------------------------------------

[DELETED].

[DELETED].

b.  Vesting: Dialysis Center's [DELETED] will vest [DELETED], and will be paid
    in accordance with the terms and conditions described above.

                                      -12-
<PAGE>

                              Amendment #3 to Agreement No. 19990110 (Continued)
--------------------------------------------------------------------------------

                Appendix B: List of Dialysis Center Affiliates

                               (See Referenced)

                                      -13-
<PAGE>

                              Amendment #3 to Agreement No. 19990110 (Continued)
-------------------------------------------------------------------------------

                  Appendix C: List of Authorized Wholesalers

To ensure you receive the appropriate discount, it is important that we have
your current list of Authorized Wholesalers. The following list represents the
Wholesalers Amgen currently has associated with your contract. Please update the
list by adding or deleting Wholesalers as necessary.

[DELETED]

                                      -14-
<PAGE>

                              Amendment #3 to Agreement No. 19990110 (Continued)
-------------------------------------------------------------------------------

                                                                      Exhibit #1
                             Certification Letter
                             --------------------

Month X, 2001

Total Renal Care, Inc.
21250 Hawthorne Boulevard, Suite 800
Torrance, CA  90503

RE:  EPOGEN(R)(Epoetin alfa) Agreement No. 19990110

Dear [DELETED]:

Thank you for your participation in the [DELETED]. In order for us to process
your data, we require that a duly authorized representative of your organization
sign the certification below.

Upon receipt of this executed document, we will calculate the value of your
incentive. If we do not receive the executed certification, we cannot provide
you with this incentive.

If you have any questions regarding this letter please contact me at [DELETED].
Thank you for your assistance in returning this certification.

Sincerely,

[DELETED]
[DELETED] Incentive Analyst

CERTIFICATION:

On behalf of Total Renal Care, Inc. and all eligible Affiliates participating in
the [DELETED] under Agreement No. 19990110, the undersigned hereby certifies
that the [DELETED] data and any other data required to be submitted (herein
referred to as "Data"), for each eligible Affiliate during the term of this
Agreement shall include the required Data from all dialysis patients from each
such Affiliate, [DELETED], and shall not include Data from non-patients. The
party executing this document also represents and warrants that it (i) has no
reason to believe that the submitted Data will be incorrect, and (ii) is
authorized to make this certification on behalf of all eligible Affiliates
submitting Data.

Signature:     /s/ Richard K. Whitney
               -----------------------------
Print Name:    Richard K. Whitney
               -----------------------------
Print Title:   CFO
               -----------------------------
Date:          1/17/01
               -----------------------------

                                      -15-

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