Document:

<PAGE>   1

                                                                    EXHIBIT 4.49

                                                                  EXECUTION COPY
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                               GUARANTEE AGREEMENT

                                     Between

                            FRESENIUS MEDICAL CARE AG
                                 (as Guarantor)

                                       AND

                       STATE STREET BANK AND TRUST COMPANY
                                  (as Trustee)

                                   dated as of

                                  June 15, 2001

================================================================================

<PAGE>   2

                             CROSS-REFERENCE TABLE*

<TABLE>
<CAPTION>
                  SECTION OF                                             SECTION OF
                  TRUST INDENTURE ACT                                    GUARANTEE
                  OF 1939. AS AMENDED                                    AGREEMENT
                  -------------------                                    ----------
<S>               <C>                                                    <C>
                  310(a)...............................................  4.1(a)
                  310(b) ..............................................  4.1(c),2.8
                  310(c) ..............................................  Inapplicable
                  311 (a) .............................................  2.2(b)
                  311 (b) .............................................  2.2(b)
                  311 (c) .............................................  Inapplicable
                  312(a) ..............................................  2.2(a)
                  312(b) ..............................................  2.2(b)
                  313 .................................................  2.3
                  314(a) ..............................................  2.4
                  314(b) ..............................................  Inapplicable
                  314(c) ..............................................  2.5
                  314(d) ..............................................  Inapplicable
                  314(e) ..............................................  1.1, 2.5, 3.2
                  314(f)...............................................  2.1, 3.2
                  315(a) ..............................................  3.1(d)
                  315 (b) .............................................  2.7
                  315 (c) .............................................  3.1
                  315(d) ..............................................  3.1 (d)
                  316(a) ..............................................  1.1, 2.6, 5.4
                  316(b) ..............................................  5.3
                  316(c) ..............................................  8.2
                  317(a) ..............................................  Inapplicable
                  317(b) ..............................................  Inapplicable
                  318(a) ..............................................  2.1(b)
                  318(b) ..............................................  2.1
                  318(c) ..............................................  2.1(a)
</TABLE>

------------
* This Cross-Reference Table does not constitute part of the Guarantee Agreement
and shall not affect the interpretation of any of its terms or provisions.

                                       i
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<TABLE>
<CAPTION>
                                    ARTICLE I

                                   DEFINITIONS

<S>                                                                            <C>
Section 1.1 Definitions..........................................................1

                                   ARTICLE II

                               TRUST INDENTURE ACT

Section 2.1 Trust Indenture Act, Application.....................................4
Section 2.2 List of Holders......................................................4
Section 2.3 Reports by the Guarantee Trustee.....................................5
Section 2.4 Periodic Reports to the Guarantee Trustee............................5
Section 2.5 Evidence of Compliance with Conditions Precedent.....................5
Section 2.6 Events of Default; Waiver............................................5
Section 2.7 Event of Default; Notice.............................................5
Section 2.8 Conflicting Interests................................................6

                                   ARTICLE III

               POWERS, DUTIES AND RIGHTS OF THE GUARANTEE TRUSTEE

Section 3.1 Powers and Duties of the Guarantee Trustee...........................6
Section 3.2 Certain Rights of Guarantee Trustee..................................7
Section 3.3 Compensation, Indemnity, Fees........................................9

                                   ARTICLE IV

                                GUARANTEE TRUSTEE

Section 4.1 Guarantee Trustee: Eligibility.......................................9
Section 4.2 Appointment, Removal and Resignation of the Guarantee Trustee.......10

                                    ARTICLE V

                                    GUARANTEE

Section 5.1 Guarantee...........................................................10
Section 5.2 Waiver of Notice and Demand.........................................11
Section 5.3 Obligations Not Affected............................................11
Section 5.4 Rights of Holders...................................................12
Section 5.5 Guarantee of Payment................................................12
Section 5.6 Subrogation.........................................................12
Section 5.7 Independent Obligations.............................................12
</TABLE>

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<TABLE>
<CAPTION>
                                   ARTICLE VI

                                  SUBORDINATION

<S>                                                                            <C>
Section 6.1 Subordination.......................................................13

                                   ARTICLE VII

                                   TERMINATION

Section 7.1 Termination.........................................................14

                                  ARTICLE VIII

                                  MISCELLANEOUS

Section 8.1 Successors and Assigns..............................................14
Section 8.2 Amendments..........................................................14
Section 8.3 Notices.............................................................15
Section 8.4 Benefit.............................................................16
Section 8.5 Interpretation......................................................16
Section 8.6 Governing Law.......................................................16
Section 8.7 Consent to Jurisdiction.............................................17
Section 8.8 Counterparts........................................................17

EXHIBIT A -Form of Guarantee Agreement with respect to the Common Securities
</TABLE>

                                      iii
<PAGE>   5

                               GUARANTEE AGREEMENT

         This GUARANTEE AGREEMENT, dated as of June 15, 2001, is executed and
delivered by FRESENIUS MEDICAL CARE AG, a stock corporation (Aktiengesellschaft)
organized under the laws of the Federal Republic of Germany (the "Guarantor"),
having its principal office at Else-Kroner Strasse 1, 61346 Bad Homburg v.d.H.,
Germany, and STATE STREET BANK AND TRUST COMPANY, a Massachusetts chartered
trust company, as trustee (the "Guarantee Trustee"), for the benefit of the
Holders (as defined herein) from time to time of the Preferred Securities (as
defined herein) of Fresenius Medical Care Capital Trust V, a Delaware business
trust (the "Trust").

         WHEREAS, pursuant to a Declaration of Trust dated as of June 1, 2001
(as amended and restated, the "Declaration"), the Trust is issuing Euro
300,000,000 aggregate liquidation amount of its 7 3/8% Trust Preferred
Securities, liquidation amount Euro 1,000 per preferred security (the "Preferred
Securities") representing preferred undivided beneficial interests in the assets
of the Trust and having the terms set forth in the Declaration;

         WHEREAS, the Preferred Securities will be issued by the Trust and the
proceeds thereof, together with the proceeds from the issuance of the Trust's
Common Securities (as defined below), will be used to purchase the Notes (as
defined in the Declaration) of the Issuer (as defined in the Declaration) which
will be held by State Street Bank and Trust Company, as Preferred Trustee under
the Declaration, as trust assets;

         WHEREAS, the Guarantor has agreed to separately guarantee the
obligations of the Trust with respect to the Common Securities (as herein
defined) (Exhibit A); and

         WHEREAS, as incentive for the Holders to purchase Preferred Securities
the Guarantor desires irrevocably and unconditionally to guarantee, to the
extent set forth herein, payment to the Holders of the Preferred Securities of
the Guarantee Payments (as defined herein) and to make certain other payments on
the terms and conditions set forth herein.

         NOW, THEREFORE, in consideration of the purchase by each Holder of
Preferred Securities, which purchase the Guarantor hereby agrees shall benefit
the Guarantor, the Guarantor executes and delivers this Guarantee Agreement for
the benefit of the Holders from time to time of the Preferred Securities.

                                    ARTICLE I
                                   DEFINITIONS

         .1 Definitions.

         As used in this Guarantee Agreement, the terms set forth below shall,
unless the context otherwise requires, have the following meanings. Capitalized
or otherwise defined terms used but not otherwise defined herein shall have the
meanings assigned to such terms in the Declaration as in effect on the date
hereof.

         "Affiliate" of any specified Person means any other Person directly or
indirectly

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controlling or controlled by or under direct or indirect common control with
such specified Person, provided, however, that an Affiliate of the Guarantor
shall not be deemed to include the Trust, Fresenius Medical Care Capital Trust,
a Delaware business trust, Fresenius Medical Care Capital Trust II, a Delaware
business trust, Fresenius Medical Care Capital Trust III, a Delaware business
trust, Fresenius Medical Care Capital Trust IV, a Delaware business trust, or
any business trust organized and operated on such similar terms. For the
purposes of this definition, "control" when used with respect to any specified
Person means the power to direct the management and policies of such Person,
directly or indirectly, whether through the ownership of voting securities, by
contract or otherwise; and the terms "controlling" and "controlled" have
meanings correlative to the foregoing.

         "Common Security" means an undivided beneficial interest in the assets
of the Trust, having a Liquidation Amount (as defined in the Declaration) of
(pounds sterling)1,000 and having the rights provided therefor in the
Declaration, including the right to receive Distributions and a Liquidation
Distribution as provided therein.

         "Event of Default" means a default by the Guarantor on any of its
payment obligations under this Guarantee Agreement; provided, however, that,
except with respect to a default in payment of any Guarantee Payments, the
Guarantor shall have received notice of default and shall not have cured such
default within 60 days after receipt of such notice.

         "Exchange Guarantee Agreement" means the guarantee agreement, as
amended, modified or supplemented from time to time, to be executed and
delivered by the Guarantor and the Guarantee Trustee as contemplated by the
Registration Rights Agreement.

         "Guarantee Agreement" means the Initial Guarantee Agreement, and when
and if issued, the Exchange Guarantee Agreement.

         "Guarantee Payments" means the following payments or distributions,
without duplication, with respect to the Preferred Securities, to the extent not
paid or made by or on behalf of the Trust; (i) any accumulated and unpaid
Distributions (as defined in the Declaration) required to be paid on the
Preferred Securities, to the extent the Trust shall have funds on hand legally
available therefor at such time, (ii) the Redemption Price (as defined in the
Declaration) with respect to the Preferred Securities called for redemption by
the Trust, to the extent the Trust shall have funds on hand legally available
therefor at such time, and (iii) upon a voluntary or involuntary dissolution,
winding up or liquidation of the Trust, unless Notes are distributed to the
Holders, the lesser of (a) the aggregate of the liquidation amount of (pounds
sterling)1,000 per Preferred Security plus accrued and unpaid Distributions on
the Preferred Securities to the date of payment, to the extent the Trust shall
have funds on hand legally available to make such payment at such time and (b)
the amount of assets of the Trust remaining legally available for distribution
to Holders upon liquidation of the Trust (in either case, the "Liquidation
Distribution").

         "Guarantee Trustee" means State Street Bank and Trust Company, until a
Successor Guarantee Trustee has been appointed and has accepted such appointment
pursuant to the terms of this Guarantee Agreement and thereafter means each such
Successor Guarantee Trustee.

                                       2
<PAGE>   7

         "Holder" means any Holder (as defined in the Declaration) of any
Preferred Securities; provided, however, that in determining whether the holders
of the requisite percentage of Preferred Securities have given any request,
demand, authorization, direction, notice, consent or waiver hereunder, "Holder"
shall not include the Guarantor, any Trustee (other than the Guarantee Trustee
acting in a capacity other than its individual capacity or its capacity as
Guarantee Trustee), or any Affiliate of the Guarantor or of any Trustee (other
than the Guarantee Trustee acting in a capacity other than its individual
capacity or its capacity as Guarantee Trustee).

         "Indenture" means the Senior Subordinated Indenture dated as of June
15, 2001, among the Issuer of the Notes, as issuer, State Street Bank and Trust
Company, as trustee, and the Guarantors, as amended or supplemented from time to
time.

         "Initial Guarantee Agreement" means this Guarantee Agreement, dated as
of June 15, 2001 between the Guarantor and the Guarantee Trustee, on behalf of
and for the benefit of the Holders of the Initial Preferred Securities, as may
be modified, amended or supplemented and in effect from time to time.

         "Initial Preferred Security" means an undivided beneficial preferred
interest in the assets of the Trust, having a Liquidation Amount of (pounds
sterling)1,000 and having the rights provided therefor in the Declaration,
including the right to receive Distributions and a Liquidation Distribution, as
provided therein.

         "List of Holders" has the meaning specified in Section 2.2(a).

         "Majority in liquidation amount of the Securities" means, except as
provided by the Trust Indenture Act, a vote by the Holders of more than 50% of
the aggregate Liquidation Amount of all Preferred Securities then Outstanding.

         "Officers' Certificate" means, a certificate signed by the Chief
Executive Officer and/or Chief Financial Officer and a Member of the Managing
Board of the Guarantor, and delivered to the appropriate Trustee. Any Officers'
Certificate delivered with respect to compliance with a condition or covenant
provided for in this Guarantee Agreement shall include:

                  (a) a statement that each officer signing the Officers'
Certificate has read the covenant or condition and the definitions relating
thereto;

                  (b) a brief statement of the nature and scope of the
examination or investigation undertaken by each officer in rendering the
Officers' Certificate;

                  (c) a statement that each officer has made such examination or
investigation as, in such officer's opinion, is necessary to enable such officer
to express an informed opinion as to whether or not such covenant or condition
has been complied with; and

                  (d) a statement as to whether, in the opinion of each officer,
such condition or covenant has been complied with.

                                       3
<PAGE>   8

         "Person" means any individual, corporation, partnership, joint venture,
association, joint-stock company, trust, unincorporated organization, government
or any agency, instrumentality or political subdivision thereof, or any other
entity.

         "Responsible Officer" means, with respect to the Guarantee Trustee, any
Senior Vice President, any Vice President, any Assistant Vice President, the
Secretary, any Assistant Secretary, the Treasurer, any Assistant Treasurer, any
Trust Officer or Assistant Trust Officer or any other officer of the Corporate
Trust Department of the above-designated officers and also means, with respect
to a particular corporate trust matter, any other officer to whom such matter is
referred because of that officer's knowledge of and familiarity with the
particular subject.

         "Senior Indebtedness" has the meaning specified in the Indenture.

         "Successor Guarantee Trustee" means a successor Guarantee Trustee
possessing the qualifications to act as Guarantee Trustee under Section 4.1.

         "Trust Indenture Act" means the Trust Indenture Act of 1939 as in force
at the date as of which this instrument was executed; provided, however, that in
the event the Trust Indenture Act of 1939 is amended after such date, "Trust
Indenture Act" means, to the extent required by any such amendment, the Trust
Indenture Act of 1939 as so amended.

                                   ARTICLE II
                               TRUST INDENTURE ACT

         .1 Trust Indenture Act, Application.

                  (a) This Guarantee Agreement shall be subject to and be
governed by the Trust Indenture Act upon the consummation of the Exchange Offer
pursuant to the Registration Rights Agreement. Until such Exchange Offer, the
Trust Indenture Act shall not apply to this Guarantee Agreement, except to the
extent otherwise expressly provided herein.

                  (b) Except as otherwise expressly provided herein, if and to
the extent that any provision of this Guarantee Agreement limits, qualifies or
conflicts with the duties imposed by Sections 310 to 317, inclusive, of the
Trust Indenture Act, such imposed duties shall control.

         .2 List of Holders.

                  (a) The Guarantor shall furnish or cause to be furnished to
the Guarantee Trustee (a) semiannually, on or before January 15 and July 15 of
each year, a list, in such form as the Guarantee Trustee may reasonably require,
of the names and addresses of the Holders ("List of Holders") as of a date not
more than 15 days prior to the delivery thereof, and (b) at such other times as
the Guarantee Trustee may request in writing, within 30 days after the receipt
by the Guarantor of any such request, a List of Holders as of a date not more
than 15 days prior to the time such list is furnished, in each case to the
extent such information is in the possession or control of the Guarantor and is
not identical to a previously supplied list of Holders or has not otherwise been
received by the Guarantee Trustee in its capacity as such. The Guarantee Trustee
may destroy any List of Holders previously given to it on receipt of a new List
of Holders.

                                       4
<PAGE>   9

                  (b) The Guarantee Trustee shall comply with its obligations
under Section 311(a), Section 311(b) and Section 312(b) of the Trust Indenture
Act.

         .3 Reports by the Guarantee Trustee.

         Not later than July 15 of each year, commencing July 15, 2002, the
Guarantee Trustee shall provide to the Holders such reports as are required by
Section 313 of the Trust Indenture Act (in the case of the initial report, with
respect to the period beginning on the Closing Date), if any, in the form and in
the manner provided by Section 313 of the Trust Indenture Act. The Guarantee
Trustee shall also comply with the requirements of Section 31 3(d) of the Trust
Indenture Act.

         .4 Periodic Reports to the Guarantee Trustee.

         The Guarantor shall provide to the Guarantee Trustee, the Securities
and Exchange Commission and the Holders such documents, reports and information,
if any, as required by Section 314 of the Trust Indenture Act and the compliance
certificate required by Section 314 of the Trust Indenture Act, in the form, in
the manner and at the times required by Section 314 of the Trust Indenture Act.

         .5 Evidence of Compliance with Conditions Precedent.

         The Guarantor shall provide to the Guarantee Trustee such evidence of
compliance with such conditions precedent, if any, provided for in this
Guarantee Agreement that relate to any of the matters set forth in Section
314(c) of the Trust Indenture Act. Any certificate or opinion required to be
given by an officer pursuant to Section 314(c)(1) may be given in the form of an
Officers' Certificate.

         .6 Events of Default; Waiver.

         The Holders of a Majority in liquidation amount of the Preferred
Securities may, by vote, on behalf of the Holders, waive any past Event of
Default and its consequences. Upon such waiver, any such Event of Default shall
cease to exist, and any Event of Default arising therefrom shall be deemed to
have been cured, for every purpose of this Guarantee Agreement, but no such
waiver shall extend to any subsequent or other default or Event of Default or
impair any right consequent therefrom.

         .7 Event of Default; Notice.

                  (a) The Guarantee Trustee shall, within 90 days after the
occurrence of an Event of Default, transmit by mail, first class postage
prepaid, to the Holders, notices of all Events of Default known to the Guarantee
Trustee, unless such defaults have been cured before the giving of such notice,
provided, that, except in the case of a default in the payment of a Guarantee
Payment, the Guarantee Trustee shall be protected in withholding such notice if
and so long as the board of directors, the executive committee or a trust
committee of directors and/or Responsible Officers of the Guarantee Trustee in
good faith determines that the withholding of such notice is in the interests of
the Holders.

                                       5
<PAGE>   10

                  (b) The Guarantee Trustee shall not be deemed to have
knowledge of any Event of Default unless the Guarantee Trustee shall have
received written notice, or a Responsible Officer charged with the
administration of the Declaration shall have obtained written notice, of such
Event of Default.

         .8 Conflicting Interests.

         The Declaration and the Indenture as well as the Guarantee Agreements,
Declarations and Indentures relating to the 9% Trust Preferred Securities due
2006 of Fresenius Medical Capital Trust, the 7 7/8% USD Trust Preferred
Securities due 2008 of Fresenius Medical Care Capital Trust II, the 7 3/8% DM
Trust Preferred Securities due 2008 of Fresenius Medical Care Capital Trust III
and the 7 7/8% USD Trust Preferred Securities due 2011 of Fresenius Medical Care
Capital Trust IV shall be deemed to be specifically described in this Guarantee
Agreement for the purposes of clause (i) of the first proviso contained in
Section 310(b) of the Trust Indenture Act.

                                   ARTICLE III
               POWERS, DUTIES AND RIGHTS OF THE GUARANTEE TRUSTEE

         .1 Powers and Duties of the Guarantee Trustee.

                  (a) This Guarantee Agreement shall be held by the Guarantee
Trustee for the benefit of the Holders, and the Guarantee Trustee shall not
transfer this Guarantee Agreement to any Person except a Holder exercising his
or her rights pursuant to Section 5.4(iv) or to a Successor Guarantee Trustee on
acceptance by such Successor Guarantee Trustee of its appointment to act as
Successor Guarantee Trustee. The right, title and interest of the Guarantee
Trustee shall automatically vest in any Successor Guarantee Trustee, upon
acceptance by such Successor Guarantee Trustee of its appointment hereunder, and
such vesting and cessation of title shall be effective whether or not
conveyancing documents have been executed and delivered pursuant to the
appointment of such Successor Guarantee Trustee.

                  (b) If an Event of Default has occurred and is continuing, the
Guarantee Trustee shall enforce this Guarantee Agreement for the benefit of the
Holders.

                  (c) The Guarantee Trustee, before the occurrence of any Event
of Default and after the curing of all Events of Default that may have occurred,
shall undertake to perform only such duties as are specifically set forth in
this Guarantee Agreement, and no implied covenants shall be read into this
Guarantee Agreement against the Guarantee Trustee. In case an Event of Default
has occurred (that has not been cured or waived pursuant to Section 2.6), the
Guarantee Trustee shall exercise such of the rights and powers vested in it by
this Guarantee Agreement, and use the same degree of care and skill in its
exercise thereof, as a prudent person would exercise or use under the
circumstances in the conduct of his or her own affairs.

                  (d) No provision of this Guarantee Agreement shall be
construed to relieve the Guarantee Trustee from liability for its own negligent
action its own negligent failure to act or its own willful misconduct, except
that:

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<PAGE>   11

                           (i) prior to the occurrence of any Event of Default
         and after the curing or waiving of all such Events of Default that may
         have occurred:

                                    (A) the duties and obligations of the
                  Guarantee Trustee shall be determined solely by the express
                  provisions of this Guarantee Agreement (including pursuant to
                  Section 2.1), and the Guarantee Trustee shall not be liable
                  except for the performance of such duties and obligations as
                  are specifically set forth in this Guarantee Agreement; and

                                    (B) in the absence of bad faith on the part
                  of the Guarantee Trustee, the Guarantee Trustee may
                  conclusively rely, as to the truth of the statements and the
                  correctness of the opinions expressed therein, upon any
                  certificates or opinions furnished to the Guarantee Trustee
                  and conforming to the requirements of this Guarantee
                  Agreement; but in the case of any such certificates or
                  opinions that by any provision hereof or of the Trust
                  Indenture Act are specifically required to be furnished to the
                  Guarantee Trustee, the Guarantee Trustee shall be under a duty
                  to examine the same to determine whether or not they conform
                  to the requirements of this Guarantee Agreement;

                           (ii) the Guarantee Trustee shall not be liable for
         any error of judgment made in good faith by a Responsible Officer of
         the Guarantee Trustee, unless it shall be proved that the Guarantee
         Trustee was negligent in ascertaining the pertinent facts upon which
         such judgment was made;

                           (iii) the Guarantee Trustee shall not be liable with
         respect to any action taken or omitted to be taken by it in good faith
         in accordance with the direction of the Holders of not less than a
         Majority in liquidation amount of the Preferred Securities relating to
         the time, method and place of conducting any proceeding for any remedy
         available to the Guarantee Trustee, or exercising any trust or power
         conferred upon the Guarantee Trustee under this Guarantee Agreement;
         and

                           (iv) no provision of this Guarantee Agreement shall
         require the Guarantee Trustee to expend or risk its own funds or
         otherwise incur personal financial liability in the performance of any
         of its duties or in the exercise of any of its rights or powers, if the
         Guarantee Trustee shall have reasonable grounds for believing that the
         repayment of such funds or liability is not reasonably assured to it
         under the terms of this Guarantee Agreement or adequate indemnity
         against such risk or liability is not reasonably assured to it.

         .2 Certain Rights of Guarantee Trustee.

                  (a) Subject to the provisions of Section 3.1:

                           (i) The Guarantee Trustee may rely and shall be fully
         protected in acting or refraining from acting upon any resolution,
         certificate, statement, instrument, opinion, report, notice, request,
         direction, consent, order, bond, debenture, note, other evidence of

                                       7
<PAGE>   12

         indebtedness or other paper or document reasonably believed by it to be
         genuine and to have been signed, sent or presented by the proper party
         or parties.

                           (ii) Any direction or act of the Guarantor
         contemplated by this Guarantee Agreement shall be sufficiently
         evidenced by an Officers' Certificate unless otherwise prescribed
         herein.

                           (iii) Whenever, in the administration of this
         Guarantee Agreement, the Guarantee Trustee shall deem it desirable that
         a matter be proved or established before taking, suffering or omitting
         to take any action hereunder, the Guarantee Trustee (unless other
         evidence is herein specifically prescribed) may, in the absence of bad
         faith on its part, request and rely upon an Officers' Certificate
         which, upon receipt of such request from the Guarantee Trustee, shall
         be promptly delivered by the Guarantor.

                           (iv) The Guarantee Trustee may consult with legal
         counsel, and the written advice or opinion of such legal counsel with
         respect to legal matters shall be full and complete authorization and
         protection in respect of any action taken, suffered or omitted to
         betaken by it hereunder in good faith and in accordance with such
         advice or opinion. Such legal counsel may be legal counsel to the
         Guarantor or any of its Affiliates and may be one of its employees. The
         Guarantee Trustee shall have the right at any time to seek instructions
         concerning the administration of this Guarantee Agreement from any
         court of competent jurisdiction subject to Section 8.7 hereof.

                           (v) The Guarantee Trustee shall be under no
         obligation to exercise any of the rights or powers vested in it by this
         Guarantee Agreement at the request or direction of any Holder, unless
         such Holder shall have provided to the Guarantee Trustee such adequate
         security and indemnity as would satisfy a reasonable person in the
         position of the Guarantee Trustee, against the costs, expenses
         (including attorneys' fees and expenses) and liabilities that might be
         incurred by it in complying with such request or direction, including
         such reasonable advances as may be requested by the Guarantee Trustee;
         provided that, nothing contained in this Section 3.2(a)(v) shall be
         taken to relieve the Guarantee Trustee, upon the occurrence of an Event
         of Default, of its obligation to exercise the rights and powers vested
         in it by this Guarantee Agreement.

                           (vi) The Guarantee Trustee shall not be bound to make
         any investigation into the facts or matters stated in any resolution,
         certificate, statement, instrument, opinion, report, notice, request,
         direction, consent, order, bond, debenture, note, other evidence of
         indebtedness or other paper or document, but the Guarantee Trustee, in
         its discretion, may make such further inquiry or investigation into
         such facts or matters as it may see fit.

                           (vii) The Guarantee Trustee may execute any of the
         trusts or powers hereunder or perform any duties hereunder either
         directly or by or through its agents or attorneys, and the Guarantee
         Trustee shall not be responsible for any misconduct or negligence on
         the part of any such agent or attorney appointed with due care by it
         hereunder.

                                       8
<PAGE>   13

                           (viii) Whenever in the administration of this
         Guarantee Agreement the Guarantee Trustee shall deem it desirable to
         receive instructions with respect to enforcing any remedy or right or
         taking any other action hereunder, the Guarantee Trustee (A) may
         request instructions from the Holders, (B) may refrain from enforcing
         such remedy or right or taking such other action until such
         instructions are received, and (C) shall be protected in acting in
         accordance with such instructions.

                  (b) No provision of this Guarantee Agreement shall be deemed
to impose any duty or obligation on the Guarantee Trustee to perform any act or
acts or exercise any right, power, duty or obligation conferred or imposed on it
in any jurisdiction in which it shall be illegal, or in which the Guarantee
Trustee shall be unqualified or incompetent in accordance with applicable law,
to perform any such act or acts or to exercise any such right, power, duty or
obligation. No permissive power or authority available to the Guarantee Trustee
shall be construed to be a duty to act in accordance with such power and
authority.

         .3 Compensation, Indemnity, Fees.

         The Guarantor agrees:

                           (i) to pay to the Guarantee Trustee from time to time
         reasonable compensation for all services rendered by it hereunder
         (which compensation shall not be limited by any provisions of law in
         regard to the compensation of a trustee of an express trust);

                           (ii) except as otherwise expressly provided herein,
         to reimburse the Guarantee Trustee upon request for all reasonable
         expenses, disbursements and advances incurred or made by the Guarantee
         Trustee in accordance with any provision of this Guarantee Agreement
         (including the reasonable compensation and the expenses and
         disbursements of its agents and counsel), except any such expense,
         disbursement or advance as may be attributable to its negligence or bad
         faith; and

                           (iii) to indemnify the Guarantee Trustee for, and to
         hold it harmless against, any loss, liability or expense incurred
         without negligence or bad faith on the part of the Guarantee Trustee,
         arising out of or in connection with the acceptance or administration
         of this Guarantee Agreement, including the costs and expenses of
         defending itself against any claim or liability in connection with the
         exercise or performance of any of its powers or duties hereunder.

         The Guarantee Trustee will not claim or exact any lien or charge on any
Guarantee Payments as a result of any amount due to it under this Guarantee
Agreement. The provisions of this Section 3.3 shall survive the termination of
this Guarantee Agreement or the resignation or removal of the Guarantee Trustee.

                                   ARTICLE IV
                                GUARANTEE TRUSTEE

         .1 Guarantee Trustee: Eligibility.

                                       9
<PAGE>   14

                  (a) There shall at all times be a Guarantee Trustee which
shall:

                           (i) not be an Affiliate of the Guarantor; and

                           (ii) be a Person that is eligible pursuant to the
         Trust Indenture Act to act as such and has a combined capital and
         surplus of at least $50,000,000,and shall be a corporation meeting the
         requirements of Section 310(c) of the Trust Indenture Act. If such
         corporation publishes reports of condition at least annually, pursuant
         to law or to the requirements of the supervising or examining
         authority, then, for the purposes of this Section 4.1 and to the extent
         permitted by the Trust Indenture Act, the combined capital and surplus
         of such corporation shall be deemed to be its combined capital and
         surplus as set forth in its most recent report of condition so
         published.

                  (b) If at any time the Guarantee Trustee shall cease to be
eligible to so act under Section 4.1(a), the Guarantee Trustee shall immediately
resign in the manner and with the effect set out in Section 4.2.

                  (c) If the Guarantee Trustee has or shall acquire any
"conflicting interest" within the meaning of Section 310(b) of the Trust
Indenture Act, the Guarantee Trustee and Guarantor shall in all respects comply
with the provisions of Section 310(b) of the Trust Indenture Act.

         .2 Appointment, Removal and Resignation of the Guarantee Trustee.

                  (a) Subject to Section 4.2(b), the Guarantee Trustee may be
appointed or removed without cause at any time a by the Guarantor.

                  (b) The Guarantee Trustee shall not be removed until a
Successor Guarantee Trustee has been appointed and has accepted such appointment
by written instrument executed by such Successor Guarantee Trustee and delivered
to the Guarantor.

                  (c) The Guarantee Trustee appointed hereunder shall hold
office until a Successor Guarantee Trustee shall have been appointed or until
its removal or resignation. The Guarantee Trustee may resign from office
(without need for prior or subsequent accounting) by an instrument in writing
executed by the Guarantee Trustee and delivered to the Guarantor, which
resignation shall not take effect until a Successor Guarantee Trustee has been
appointed and has accepted such appointment by instrument in writing executed by
such Successor Guarantee trustee and delivered to the Guarantor and the
resigning Guarantee Trustee.

                  (d) If no Successor Guarantee Trustee shall have been
appointed and accepted appointment as provided in this Section 4.2 within 60
days after delivery to the Guarantor of an instrument of resignation, the
resigning Guarantee Trustee may petition, at the expense of the Guarantor, any
court of competent jurisdiction for appointment of a Successor Guarantee
Trustee. Such court may thereupon, after prescribing such notice, if any, as it
may deem proper, appoint a Successor Guarantee Trustee.

                                    ARTICLE V
                                    GUARANTEE

                                       10
<PAGE>   15

         .1 Guarantee.

         The Guarantor irrevocably and unconditionally agrees to pay in full on
a senior subordinated basis, to the extent set forth herein, to the Holders the
Guarantee Payments (without duplication of amounts theretofore paid by or on
behalf of the Trust), as and when due regardless of any defense, right of
set-off or counterclaim which the Trust may have or assert, other than the
defense of payment. The Guarantor's obligation to make a Guarantee Payment may
be satisfied by direct payment of the required amounts by the Guarantor to the
Holders or by causing the Trust to pay such amounts to the Holders.

         .2 Waiver of Notice and Demand.

         The Guarantor hereby waives notice of acceptance of the Guarantee
Agreement and of any liability to which it applies or may apply, presentment,
demand for payment, any right to require a proceeding first against the
Guarantee Trustee, the Trust or any other Person before proceeding against the
Guarantor, protest, notice of nonpayment, notice of dishonor, notice of
redemption and all other notices and demands.

         .3 Obligations Not Affected.

         The obligations, covenants, agreements and duties of the Guarantor
under this Guarantee Agreement shall in no way be affected or impaired by reason
of the happening from time to time of any of the following:

                  (a) the release or waiver, by operation of law or otherwise,
of the performance or observance by the Trust of any express or implied
agreement, covenant, term or condition relating to the Preferred Securities to
be performed or observed by the Trust;

                  (b) the extension of time for the payment by the Trust of all
or any portion of the Distributions, Redemption Price, Liquidation Distribution
or any other sums payable under the terms of the Preferred Securities or the
extension of time for the performance of any other obligation under, arising out
of, or in connection with, the Preferred Securities;

                  (c) any failure, omission, delay or lack of diligence on the
part of the Holders to enforce, assert or exercise any right, privilege, power
or remedy conferred on the Holders pursuant to the terms of the Preferred
Securities, or any action on the part of the Trust granting indulgence or
extension of any kind;

                  (d) the voluntary or involuntary liquidation, dissolution,
sale of any collateral, receivership, insolvency, bankruptcy, assignment for the
benefit of creditors, reorganization, arrangement, composition or readjustment
of debt of, or other similar proceedings affecting, the Trust or any of the
assets of the Trust;

                  (e) any invalidity of, or defect or deficiency in, the
Preferred Securities;

                  (f) the settlement or compromise of any obligation guaranteed
hereby or hereby incurred; or

                                       11
<PAGE>   16

                  (g) any other circumstance whatsoever that might otherwise
constitute a legal or equitable discharge or defense of a guarantor, it being
the intent of this Section 5.3 that the obligations of the Guarantor hereunder
shall be absolute and unconditional under any and all circumstances.

         There shall be no obligation of the Holders to give notice to, or
obtain the consent of, the Guarantor with respect to the happening of any of the
foregoing.

         .4 Rights of Holders.

         The Guarantor expressly acknowledges that: (i) this Guarantee Agreement
will be deposited with the Guarantee Trustee to be held for the benefit of the
Holders; (ii) the Guarantee Trustee has the right to enforce this Guarantee
Agreement on behalf of the Holders; (iii) the Holders of a Majority in
liquidation amount of the Preferred Securities have the right to direct the
time, method and place of conducting any proceeding for any remedy available to
the Guarantee Trustee in respect of this Guarantee Agreement or exercising any
trust or power conferred upon the Guarantee Trustee under this Guarantee
Agreement; and (iv) upon the occurrence of an Event of Default, any Holder may
institute a legal proceeding directly against the Guarantor to enforce its
rights under this Guarantee Agreement, without first instituting a legal
proceeding against the Guarantee Trustee, the Trust or any other Person.

         .5 Guarantee of Payment.

         This Guarantee Agreement creates a guarantee of payment and not of
collection. This Guarantee Agreement will not be discharged except by payment of
the Guarantee Payments in full (without duplication of amounts theretofore paid
by the Trust out of funds legally available therefor) or upon distribution of
Notes to Holders as provided in the Declaration.

         .6 Subrogation.

         The Guarantor shall be subrogated to all (if any) rights of the Holders
against the Trust in respect of any amounts paid to the Holders by the Guarantor
under this Guarantee Agreement and shall have the right to waive payment by the
Trust pursuant to Section 5.1; provided, however, that the Guarantor shall not
(except to the extent required by mandatory provisions of law) be entitled to
enforce or exercise any rights which it may acquire by way of subrogation or any
indemnity, reimbursement or other agreement, in all cases as a result of payment
under this Guarantee Agreement, if at the time of any such payment, any amounts
are due and unpaid under this Guarantee Agreement. If any amount shall be paid
to the Guarantor in violation of the preceding sentence, the Guarantor agrees to
hold such amount in trust for the Holders and to pay over such amount to the
Holders.

         .7 Independent Obligations.

         The Guarantor acknowledges that its obligations hereunder are
independent of the obligations of the Trust with respect to the Preferred
Securities and that the Guarantor shall be liable as principal and as debtor
hereunder to make Guarantee Payments pursuant to the terms of this Guarantee
Agreement notwithstanding the occurrence of any event referred to in subsections

                                       12
<PAGE>   17

(a) through (g), inclusive, of Section 5.3 hereof.

                                   ARTICLE VI
                                  SUBORDINATION

         .1 Subordination.

                  (a) This Guarantee Agreement will constitute an unsecured
obligation of the Guarantor and will rank subordinate and junior in right of
payment to all Senior Indebtedness of the Guarantor and the Issuer.

                  (b) The Guarantor may not make a Guarantee Payment to the
Holders if (i) any Specified Senior Indebtedness (as defined in the Indenture)
of the Guarantor or any other Senior Indebtedness (as defined in the Indenture)
of the Guarantor having an outstanding principal amount at the time of
determination in excess of $25,000,000) is not paid when due or (ii) any other
default on Specified Senior Indebtedness of the Guarantor occurs and the
maturity of such Specified Senior Indebtedness is accelerated in accordance with
its terms, unless, in either case, the default has been cured or waived and any
such acceleration has been rescinded or such Specified Senior Indebtedness has
been paid in full. However, the Guarantor may make a Guarantee Payment without
regard to the foregoing if the Guarantor and the Guarantee Trustee receive
written notice approving such payment from a representative of the Specified
Senior Indebtedness with respect to which either of the events set forth in
clause (i) or (ii) of the immediately preceding sentence has occurred and is
continuing. During the continuance of any default (other than a default
described in clause (i) or (ii) of the second preceding sentence) with respect
to any Specified Senior Indebtedness of the Guarantor pursuant to which the
maturity thereof may be accelerated immediately without further notice (except
such notice as may be required to effect such acceleration) or the expiration of
any applicable grace periods, the Guarantor may not make a Guarantee Payment to
the Holders for a period (a "Payment Blockage Period," as defined in the
Indenture) commencing upon the receipt by the Guarantee Trustee (with a copy to
the Guarantor) of written notice (a "Blockage Notice," as defined in the
Indenture) of such default from the representative of the holders of such
Specified Senior Indebtedness specifying an election to effect a Payment
Blockage Period and ending 179 days thereafter (or earlier if such Payment
Blockage Period is terminated (i) by written notice to the Guarantee Trustee,
the Guarantor from the representative of the holders of such Specified Senior
Indebtedness, (ii) because the default giving rise to such Blockage Notice is no
longer continuing, as certified to the Guarantee Trustee by the representative
of the holders of such Specified Senior Indebtedness or (iii) because such
Specified Senior Indebtedness has been repaid in full, as certified to the
Guarantee Trustee by the representative of the holders of such Specified Senior
Indebtedness). Notwithstanding the provisions described in the immediately
preceding sentence, unless the holders of such Specified Senior Indebtedness or
the representative of such holders have accelerated the maturity of such
Specified Senior Indebtedness (and such Specified Senior Indebtedness remains
outstanding), the Guarantor may resume Guarantee Payments after the end of such
Payment Blockage Period. The Guarantee Agreement shall not be subject to more
than one Payment Blockage Period in any consecutive 360-day period, irrespective
of the number of defaults with respect to Specified Senior Indebtedness during
such period.

                                       13
<PAGE>   18

                  (c) Upon any payment or distribution of the assets of the
Guarantor upon a total or partial liquidation or dissolution or reorganization
of or similar proceeding relating to the Guarantor or its property, the holders
of Senior Indebtedness of the Guarantor will be entitled to receive payment in
full of such Senior Indebtedness before the Holders are entitled to receive any
Guarantee Payment, and until the Senior Indebtedness of the Guarantor is paid in
full, any payment or distribution to which the Holders would be entitled but for
this Section 6.1 will be made to holders of such Senior Indebtedness as their
interests may appear. If a Distribution is made to the Holders that, due to this
Section 6.1, should not have been made to them, such Holders are required to
hold it in trust for the holders of Senior Indebtedness of the Guarantor and pay
it over to them as their interests may appear.

                  (d) If a Guarantee Payment is to be made by the Guarantor to
the Holders, the Guarantor or the Guarantee Trustee shall promptly notify the
holders of Senior Indebtedness of the Guarantor or the representative of such
holders of such Guarantee Payment. If any Senior Indebtedness of the Guarantor
is outstanding, the Guarantor may not pay such Guarantee Payment until five
Business Days after the representatives of all the issues of Senior Indebtedness
of the Guarantor receive notice of such Guarantee Payment and, thereafter, may
pay such Guarantee Payment only if the Guarantee Agreement otherwise permits
payment at that time.

                                   ARTICLE VII
                                   TERMINATION

         .1 Termination.

         This Guarantee Agreement shall terminate and be of no further force and
effect upon (i) full payment of the Redemption Price of all Preferred
Securities, (ii) the distribution of Notes to the Holders in exchange for all of
the Preferred Securities or (iii) full payment of the amounts payable in
accordance with the Declaration upon liquidation of the Trust. Notwithstanding
the foregoing, this Guarantee Agreement will continue to be effective or will be
reinstated, as the case may be, if at any time any Holder must restore payment
of any sums paid with respect to Preferred Securities or this Guarantee
Agreement.

                                  ARTICLE VIII
                                  MISCELLANEOUS

         .1 Successors and Assigns.

         All guarantees and agreements contained in this Guarantee Agreement
shall bind the successors, assigns, receivers, trustees and representatives of
the Guarantor and shall inure to the benefit of the Holders of the Preferred
Securities then outstanding. Except in connection with a consolidation, merger
or sale involving the Guarantor that is permitted under Article VIII of the
Indenture and pursuant to which the assignee agrees in writing to perform the
Guarantor's obligations hereunder, the Guarantor shall not assign its
obligations hereunder and any purported assignment other than in accordance with
this provision shall be void.

         .2 Amendments.

                                       14
<PAGE>   19

         Except with respect to any changes which do not adversely affect the
rights of the Holders in any material respect (in which case no consent of the
Holders will be required), this Guarantee Agreement may only be amended with the
prior approval of the Holders of not less than a Majority in liquidation amount
of all the outstanding Preferred Securities. The provisions of Article VI of the
Declaration concerning meetings of the Holders shall apply to the giving of such
approval. No amendment shall be made to the definition of Guarantee Payments or
to Article V1 hereof without the consent of the requisite lenders under the Bank
Credit Agreement.

         In executing any amendment permitted by this Section, the Guarantee
Trustee shall be entitled to receive, and (subject to Section 3.1) shall be
fully protected in relying upon, an Officers' Certificate and an Opinion of
Counsel stating that the execution of such amendment is authorized or permitted
by this Guarantee Agreement, and that all conditions precedent herein provided
for relating to such action have been complied with.

         .3 Notices.

         Any notice, request or other communication required or permitted to be
given hereunder shall be in writing, duly signed by the party giving such
notice, and delivered, telecopied or mailed by first class mail as follows:

                  (a) if given to the Guarantor, to the address set forth below
or such other address, facsimile number or to the attention of such other Person
as the Guarantor may give notice to the Holders:

                  Fresenius Medical Care AG
                  Else-Kroner Strasse 1
                  61346 Bad Homburg v.d.H.
                  Germany
                  Facsimile No.: 011-49-6172-609-2103
                  Attention: Chief Executive Officer

                  (b) if given to the Trust, in care of the Guarantee Trustee,
at the Trust's (and the Guarantee Trustee's) address set forth below or such
other address as the Guarantee Trustee on behalf of the Trust may give notice to
the Holders:

                  Fresenius Medical Care Capital Trust V
                  c/o Fresenius Medical Care Holdings, Inc.
                  Two Ledgemont Center
                  95 Hayden Avenue
                  Lexington, Massachusetts 02173
                  Facsimile No.: 781-402-9714
                  Attention: Legal Department

                  with a copy to:

                  State Street Bank and Trust Company
                  225 Asylum Street

                                       15
<PAGE>   20

                  Hartford, Connecticut 06103
                  Facsimile No.: 860-244-1889
                  Attention: Corporate Trust Administration

                  (c) if given to any Holder, at the address set forth on the
books and records of the Trust.

         All notices hereunder shall be deemed to have been given when received
in person, telecopied with receipt confirmed, or mailed by first class mail,
postage prepaid, except that if a notice or other document is refused delivery
or cannot be delivered because of a changed address of which no notice was
given, such notice or other document shall be deemed to have been delivered on
the date of such refusal or inability to deliver.

         .4 Benefit.

         This Guarantee Agreement is solely for the benefit of the Holders and
is not separately transferable from the Preferred Securities.

         .5 Interpretation.

         In this Guarantee Agreement, unless the context otherwise requires:

                  (a) capitalized terms used in this Guarantee Agreement but not
defined in the preamble hereto have the respective meanings assigned to them in
Section 1.1;

                  (b) a term defined anywhere in this Guarantee Agreement has
the same meaning throughout;

                  (c) all references to "the Guarantee Agreement" or "this
Guarantee Agreement" are to this Guarantee Agreement as modified, supplemented
or amended from time to time;

                  (d) all references in this Guarantee Agreement to Articles and
Sections are to Articles and Sections of this Guarantee Agreement unless
otherwise specified;

                  (e) a term defined in the Trust Indenture Act has the same
meaning when used in this Guarantee Agreement unless otherwise defined in this
Guarantee Agreement or unless the context otherwise requires;

                  (f) a reference to the singular includes the plural and vice
versa; and

                  (g) the masculine, feminine or neuter genders used herein
shall include the masculine, feminine and neuter genders.

         .6 Governing Law.

         THIS GUARANTEE AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED AND
INTERPRETED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD
TO THE CONFLICT OF LAW PRINCIPLES

                                       16
<PAGE>   21

THEREOF.

         .7 Consent to Jurisdiction.

         The Guarantor hereby irrevocably submits to the non-exclusive
jurisdiction of any state or federal court in the Borough of Manhattan, The City
of New York, for the purpose of any suit, action, proceeding or judgment
relating to or arising out of this Guarantee Agreement. The Guarantor hereby
appoints Fresenius Medical Care Holdings, Inc., c/o CT Corporation System, with
offices on the date hereof at 1633 Broadway, New York, New York 10019, as its
authorized agent on whom process may be served in any action which may be
instituted against it by any Holder or the Guarantee Trustee in any state or
federal court in The City of New York, the Borough of Manhattan, arising out of
or relating to this Guarantee Agreement. Service of process upon such authorized
agent and written notice of such service to the Guarantor shall be deemed in
every respect effective service of process upon the Guarantor, and the Guarantor
hereby irrevocably consents to the jurisdiction of any such court in any such
action and to the laying of venue in the Borough of Manhattan, The City of New
York. The Guarantor hereby waives, to the fullest extent permitted by applicable
law, any objection to the laying of venue of any such suit, action or proceeding
brought in the aforesaid courts and hereby irrevocably waives any claim that any
such suit, action or proceeding brought in any such court has been brought in an
inconvenient forum. Notwithstanding the foregoing, nothing herein shall in any
way affect the right of the Holders of the Guarantee Trustee to bring any action
arising out of or relating to this Guarantee Agreement in any competent court
elsewhere having jurisdiction over the Guarantor and its property.

         .8 Counterparts.

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

                                       17
<PAGE>   22

         THIS GUARANTEE AGREEMENT is executed as of the day and year first above
written.

                                FRESENIUS MEDICAL CARE AG

                                By:/s/  Ben Lipps
                                   ---------------------------------------------
                                   Name: Ben Lipps
                                   Title Chief Executive Officer

                                By:/s/  Rainer Runte
                                   ---------------------------------------------
                                   Name: Rainer Runte
                                   Title: General Counsel and Sr. Vice President

                                STATE STREET BANK AND TRUST
                                COMPANY
                                   as Guarantee Trustee

                                By:/s/ Elizabeth C. Hammer
                                   ---------------------------------------------
                                   Name:  Elizabeth C. Hammer
                                   Title:  Vice President

         Acknowledged:

         FMC TRUST FINANCE S.A.R.L. LUXEMBOURG - III

         By:/s/  Gabriele Dux
            -----------------------------------------
            Name:  Gabriele Dux
            Title  Sole Manager

                                       18
<PAGE>   23

                                                                       EXHIBIT A

            GUARANTEE AGREEMENT WITH RESPECT TO THE COMMON SECURITIES

         This AGREEMENT, dated as of June 15, 2001, is executed and delivered by
FRESENIUS MEDICAL CARE AG, a stock corporation (Aktiengesellschaft) organized
under the laws of the Federal Republic of Germany ("Guarantor"), having its
principal office at Else-Kroner Strasse 1, 61346 Bad Homburg v.d.H., Germany,
for the benefit of the holders from time to time (the "Holders") of Common
Securities (as defined in the Guarantee Agreement) of Fresenius Medical Care
Capital Trust IV, a Delaware statutory business trust (the "Trust").

         WHEREAS, pursuant to the Guarantee Agreement, dated as of June 15,
2001, between Fresenius Medical Care AG, as Guarantor, and State Street Bank and
Trust Company, as Trustee (the "Guarantee Agreement"), the Guarantor has
irrevocably and unconditionally agreed to pay in full to the holders of
Preferred Securities (as defined therein) the Guarantee Payments (as defined
therein).

         WHEREAS, in order to facilitate the classification of the Trust for
United States Federal income tax purposes as a grantor trust, the benefit of the
guarantee provided by the Guarantor pursuant to the Guarantee Agreement must
inure, to the extent set forth herein, also to the benefit of the Holders.

         NOW, THEREFORE, it is hereby agreed that

         SECTION 1.0           Definitions.

         Capitalized or otherwise defined terms used but not otherwise defined
herein shall have the meanings assigned to such terms in the Guarantee Agreement
as in effect on the date hereof.

         SECTION 2.0.          Guarantee.

         The Guarantor irrevocably and unconditionally agrees to pay in full to
the Holders Guarantee Payments to the same extent as the guarantee provided to
the holders of Preferred Securities under the Guarantee Agreement; provided,
however, that upon the occurrence and during the continuation of a Declaration
Event of Default (as defined in the Declaration), holders of Preferred
Securities shall have priority over the Holders with respect to the Guarantee
Payments.

         SECTION 3.0.          Governing Law.

         THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED AND INTERPRETED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD TO THE CONFLICT
OF LAW PRINCIPLES THEREOF.

         SECTION 4.0.          Counterparts.

         This instrument may be executed in any number of counterparts, each of
which so executed shall be deemed to be an original, but all such counterparts
shall together constitute but

<PAGE>   24

one and the same instrument.

<PAGE>   25

THIS AGREEMENT is executed as of the day and year first above written.

                                FRESENIUS MEDICAL CARE AG

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:

<PAGE>   26

                                FMC TRUST FINANCE S. A.R.L. LUXEMBOURG - III

                                By:
                                   ---------------------------------------------
                                   Name:
                                   Title:

                                      S-2<PAGE>   1

                                                                    EXHIBIT 4.50

                    AGREEMENT AS TO EXPENSES AND LIABILITIES

                AGREEMENT dated as of June 6, 2001, between Fresenius Medical
Care AG, a corporation organized under the laws of Germany (the "Company"), and
Fresenius Medical Care Capital Trust IV, a Delaware business trust (the
"Trust").

                WHEREAS, the Trust intends to issue its Common Securities (the
"Common Securities") to the Company and receive 7 7/8% Senior Subordinated Notes
("Notes"; such term, for the purposes of this Agreement shall include, where
applicable the Exchange Securities as such term is defined in the Indenture)
from FMC Trust Finance S.a.r.l. Luxembourg-III (the "Issuer") and to issue and
sell 7 7/8% Preferred Securities (the "Preferred Securities"; such term, for the
purposes of this Agreement, shall include, when applicable, the Exchange
Preferred Securities) with such powers, preferences and special rights and
restrictions as are set forth in the Amended and Restated Declaration of Trust
dated as of June 6, 2001 as the same may be amended from time to time (the
"Declaration");

                WHEREAS, the Company will directly or indirectly own all of the
Common Securities of the Trust and all of the Capital Stock (as defined in the
Indenture) of the Issuer, which will issue the Notes;

                WHEREAS, capitalized terms used but not defined herein have the
meanings set forth in the Declaration.

                Now, THEREFORE, in consideration of the purchase by each Holder
of the Preferred Securities, which purchase the Company hereby agrees shall
benefit the Company and which purchase the Company acknowledges will be made in
reliance upon the execution and delivery of this Agreement, the Company and
Trust hereby agree as follows:

                                    ARTICLE I

                SECTION 1. Guarantee by the Company.

                Subject to the terms and conditions hereof, the Company hereby
irrevocably and unconditionally guarantees, on a senior subordinated basis (to
the extent and in the manner set forth in the Indenture with respect to the
Notes), to each person or entity to whom the Trust is now or hereafter becomes
indebted or liable (the "Beneficiaries") the full payment, when and as due, of
any and all Obligations (as hereinafter defined) to such Beneficiaries. As used
herein, "Obligations" means any costs, expenses or liabilities of the Trust
(including, without limitation, any and all taxes, costs and expenses, such as
underwriting discounts and commissions, payable with respect to the issuance of
the Preferred Securities), other than obligations of the Trust to pay to holders
of any Preferred Securities or other similar interests in the Trust the amounts
due such holders pursuant to the terms of the Preferred Securities or such other
similar interests, as the case may be, and United States withholding taxes. This
Agreement is intended to be for the benefit of, and to be enforceable by, all
such Beneficiaries, whether or not such Beneficiaries have received notice
hereof.

<PAGE>   2

                SECTION 1.2. Term of Agreement.

                This Agreement shall terminate and be of no further force and
effect upon the later of (a) the date on which full payment has been made of all
amounts payable to all Holders of all the Preferred Securities (whether upon
redemption, liquidation, exchange or otherwise) and (b) the date on which there
are no Beneficiaries remaining; provided, however, that this Agreement shall
continue to be effective or shall be reinstated, as the case may be, if at any
time any Holder of the Preferred Securities or any Beneficiary must restore
payment of any sums paid under the Preferred Securities, under any Obligation,
under the Guarantee Agreement dated the date hereof by the Company and State
Street Bank and Trust Company as guarantee trustee or under this Agreement for
any reason whatsoever. This Agreement is continuing, irrevocable, unconditional
and absolute.

                SECTION 1.3. Waiver of Notice.

                The Company hereby waives notice of acceptance of this Agreement
and of any Obligation to which it applies or may apply, and the Company hereby
waives presentment, demand for payment, protest, notice of nonpayment, notice of
dishonor, notice of redemption and all other notices and demands.

                SECTION 1.4. No Impairment.

                The obligations, covenants, agreements and duties of the Company
under this Agreement shall in no way be affected or impaired by reason of the
happening from time to time of any of the following:

                (a)     the extension of time for the payment by the Trust of
all or any portion of the Obligations or for the performance of any other
obligation under, arising out of, or in connection with, the Obligations;

                (b)     any failure, omission, delay or lack of diligence on the
part of the Beneficiaries to enforce, assert or exercise any right, privilege,
power or remedy conferred on the Beneficiaries with respect to the Obligations
or any action on the part of the Trust granting indulgence or extension of any
kind; or

                (c)     the voluntary or involuntary liquidation, dissolution,
sale of any collateral, receivership, insolvency, bankruptcy, assignment for the
benefit of creditors, reorganization, arrangement, composition or readjustment
of debt of, or other similar proceedings affecting, the Trust or any of the
assets of the Trust.

                There shall be no obligation of the Beneficiaries to give notice
to, or obtain the consent of, the Company with respect to the happening of any
of the foregoing.

                SECTION 1.5. Enforcement.

                A Beneficiary may enforce this Agreement directly against the
Company and the

<PAGE>   3

Company waives any right or remedy to require that any action be brought against
the Trust or any other person or entity before proceeding against the Company.
                SECTION 1.6. Subrogation.

                The Company shall be subrogated to all (if any) rights of the
Trust in respect of any amounts paid to the Beneficiaries by the Company under
this Agreement; provided, however, that the Company shall not (except to the
extent required by mandatory provisions of law) be entitled to enforce or
exercise any rights which it may acquire by way of subrogation or any indemnity,
reimbursement or other agreement, in all cases as a result of payment under this
Agreement, if, at the time of any such payment, any amounts are due and unpaid
under this Agreement.

                                   ARTICLE II

                SECTION 2.1. Assignment. Except in connection with a
consolidation, merger or sale involving the Company that is permitted under
Article VIII of the Indenture, this Agreement may not be assigned by either
party hereto without the consent of the other, and any purported assignment
without such consent shall be void.

                SECTION 2.2. Binding Effect.

                All guarantees and agreements contained in this Agreement shall
bind the successors, assigns, receivers, trustees and representatives of the
Company and shall inure to the benefit of the Beneficiaries.

                SECTION 2.3. Amendment.

                So long as there remains any Beneficiary or any Preferred
Securities are outstanding, this Agreement shall not be modified or amended in
any manner adverse to such Beneficiary or to the Holders of the Preferred
Securities without the consent of a Majority in Liquidation Amount of the
holders of Preferred Securities.

                SECTION 2.4. Notices.

                Any notice, request or other communication required or permitted
to be given hereunder shall be given in writing by delivering the same against
receipt therefor by facsimile transmission (confirmed by mail), telex or by
registered or certified mail, addressed as follows (and if so given, shall be
deemed given when mailed or upon receipt of an answer-back, if sent by telex):

                        Fresenius Medical Care Capital Trust IV
                        c/o State Street Bank and Trust Company
                        225 Asylum Street
                        Hartford, Connecticut 06103
                        Facsimile No.: 860-244-1889
                        Attention: Corporate Trust Administration

<PAGE>   4

                        Fresenius Medical Care AG
                        Else-Kroner Str. 1, 61346 Bad Homburg v.d.H., Germany
                        Facsimile No.: 011-49-6172-609-2103
                        Attention: Chief Financial Officer

                SECTION 2.5. Governing Law.

                THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED AND
INTERPRETED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT GIVING
EFFECT TO PRINCIPLES OF CONFLICT OF LAWS.

                SECTION 2.6. Submission to Jurisdiction.

                The Company hereby appoints Fresenius Medical Care Holdings,
Inc. ("FMCH") c/o CT Corporation System acting through its office at 1633
Broadway, New York, New York 10019 as its authorized agent (the "Authorized
Agent") upon which process may be served in any legal action or proceeding
against it with respect to its obligations under this Agreement instituted in
any federal or state court in the Borough of Manhattan, The City of New York, by
the Trust or a Beneficiary and agrees that service of process upon such
authorized agent, together with written notice of said service to the Company by
the person serving the same, addressed as provided in Section 2.4, shall be
deemed in every respect effective service of process upon the Company in any
such legal action or proceeding, and the Company hereby irrevocably submits to
the non-exclusive jurisdiction of any such court in respect of any such legal
action or proceeding. Such appointment shall be irrevocable until this Agreement
has been terminated in accordance with Section 1.3 hereof. Notwithstanding the
foregoing, the Company reserves the right to appoint another Person located or
with an office in the Borough of Manhattan, The City of New York, selected in
its discretion, as a successor Authorized Agent, and upon acceptance of such
appointment by such a successor the appointment of the prior Authorized Agent
shall terminate. If for any reason FMCH or CT Corporation System ceases to be
able to act as the Authorized Agent or to have an address in the Borough of
Manhattan, The City of New York, the Company will appoint a successor Authorized
Agent in accordance with the preceding sentence. The Company further agrees to
take any and all action, including the filing of any and all documents and
instruments as may be necessary to continue such designation and appointment of
such agent in full force and effect until this Agreement has been terminated in
accordance with Section 1.3 hereof. Service of process upon the Authorized Agent
addressed to it at the address set forth above, as such address may be changed
within the Borough of Manhattan, The City of New York by notice given by the
Authorized Agent to the Trustees, together with written notice of such service
mailed or delivered to the Company shall be deemed, in every respect, effective
service of process on the Company.

<PAGE>   5

                THIS AGREEMENT is executed as of the day and year first above
written.

                                FRESENIUS MEDICAL CARE AG

                                By:/s/  Ben Lipps
                                   ---------------------------------------------
                                   Name:  Ben Lipps
                                   Title: Chief Executive Officer

                                By:/s/  Rainer Runte
                                   ---------------------------------------------
                                   Name:  Rainer Runte
                                   Title: General Counsel and Senior
                                          Vice President

                                FRESENIUS MEDICAL CARE CAPITAL TRUST IV

                                By:/s/  Josef Dinger
                                   ---------------------------------------------
                                   Name:   Josef Dinger
                                   Company Trustee

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