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                                                                    EXHIBIT 4.21

                                     FORM OF

                          FIFTH SUPPLEMENTAL INDENTURE


        FIFTH SUPPLEMENTAL INDENTURE, dated as of May __, 2002 (this "Fifth
Supplemental Indenture"), among AMB PROPERTY, L.P., a Delaware limited
partnership (the "Operating Partnership"), AMB PROPERTY CORPORATION (the "Parent
Guarantor") and STATE STREET BANK AND TRUST COMPANY OF CALIFORNIA, N.A., as
Trustee hereunder (the "Trustee").

                              W I T N E S S E T H:

        WHEREAS, the Operating Partnership, the Parent Guarantor and the Trustee
executed and delivered an Indenture, dated as of June 30, 1998, as supplemented
by the First Supplemental Indenture, the Second Supplemental Indenture and the
Third Supplemental Indenture, each dated as of June 30, 1998, and the Fourth
Supplemental Indenture, dated as of August 15, 2000 (as further supplemented
hereby, the "Indenture"), to provide for the issuance by the Operating
Partnership of notes evidencing its unsecured indebtedness;

        WHEREAS, pursuant to Board Resolution, the Operating Partnership has
authorized the issuance of up to $400,000,000 of its Series B Medium-Term Notes
due nine months or more from the date of issuance;

        WHEREAS, the Operating Partnership desires to establish the terms of
such notes in accordance with Section 301 of the Indenture and to establish the
form of such notes in accordance with Section 201 of the Indenture.

                                    ARTICLE 1
                                      TERMS

        SECTION 101. TERMS OF SECURITIES. There is hereby established and
authorized for issuance by the Operating Partnership a series of Securities (as
defined in the Indenture), the terms of which shall be as follows:

               (a) The Securities of the series shall be designated "Series B
        Medium-Term Notes" (the "Notes").

               (b) The aggregate principal amount of the Notes that may be
        authenticated and delivered under the Indenture from time to time
        (except for Notes authenticated and delivered upon registration of
        transfer of, or in exchange for, or in lieu of, other Notes pursuant to
        Sections 304, 305, 306, 906, or 1107 of the Indenture) shall be up to
        $400,000,000 or the equivalent thereof in other currencies, which amount
        may be increased from time to time by a Board Resolution or a
        supplemental indenture to the Indenture or an Officers' Certificate, in
        either case, pursuant to authority granted under a Board Resolution, and
        in accordance with Section 301 of the Indenture.

               (c) Each Note shall mature on a date which shall be nine months
        or more from the date of issue of such Note and shall be specified by an
        officer of the Parent Guarantor, as general partner of the Operating
        Partnership, to the Trustee in writing or by telephone (telephonic
        instructions to be promptly confirmed in writing) and specified in the
        applicable prospectus supplement or pricing supplement.



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               (d) The interest rate or rates or the method of determination
        thereof, if any, the date or dates or the method of determination
        thereof from which such interest shall accrue, the date or dates on
        which such interest shall be payable, and the regular record date for
        the interest payable on any interest payment date, in each case for a
        particular Note, shall each be as specified by an officer of the Parent
        Guarantor, as general partner of the Operating Partnership, to the
        Trustee in writing or by telephone (telephonic instructions to be
        promptly confirmed in writing); provided, however, the interest rate or
        rates shall in no event be higher than the maximum rate permitted by New
        York law, as the same may be modified by United States law of general
        application.

               (e) Unless stated to the contrary in the applicable prospectus
        supplement or pricing supplement, the payment of principal (and premium,
        if any) and interest on, a Note on any day, if the Holder of such Note
        is The Depository Trust Company, a New York corporation (or its nominee
        or other depository, a "Depository"), will be made in accordance with
        any applicable provisions of such written agreement between the
        Operating Partnership, the Trustee and the Depository (or its nominee)
        as may be in effect from time to time. Otherwise payment of principal
        (and premium, if any) and interest on the Notes shall be payable, and
        Notes may be surrendered for the registration of transfer or exchange,
        at the office of the Trustee's affiliate, State Street Bank and Trust
        Company, at 61 Broadway, 15th Floor, New York, New York 10006, unless
        the Holder of the Note is notified otherwise; provided, however, that at
        the option of the Operating Partnership, interest may be paid by check
        mailed to the address of the person entitled thereto as such address
        shall appear in the Operating Partnership's security register or by wire
        transfer to an account maintained by the payee located in the United
        States. Unless the Holder of the Note is notified otherwise, the place
        where notices or demands to or upon the Operating Partnership in respect
        of the Notes and the Indenture may be served shall be the Corporate
        Trust Office of the Trustee at 633 West Fifth Street, 12th Floor, Los
        Angeles, California 90071.

               (f) To receive payment of a U.S. Dollar denominated Note upon
        redemption, if applicable, or at maturity, a Holder must make
        presentation and surrender of such Note on or before the Redemption Date
        or Maturity Date, if any, as specified on the face of any Note and in
        the applicable prospectus supplement or pricing supplement. To receive
        payment of a Note denominated in a Foreign Currency (as hereinafter
        defined) or composite currency upon redemption or at maturity, a Holder
        must make presentation and surrender of such Note not less than two
        Business Days (as defined in the Notes) prior to the Redemption Date or
        Maturity Date, if any, as specified on the face of any Note and in the
        applicable prospectus supplement or pricing supplement. Upon
        presentation and surrender of a Note denominated in a Foreign Currency
        or composite currency at any time after the date two Business Days prior
        to the Redemption Date or Maturity Date, if any, as specified on the
        face of any Note and in the applicable prospectus supplement or pricing
        supplement, the Operating Partnership will pay the principal amount (and
        premium, if any) of such Note, and any interest due upon redemption or
        at maturity (unless the Redemption Date or Maturity Date is an Interest
        Payment Date, as specified on the face of the Note and in the applicable
        prospectus supplement or pricing supplement), two Business Days after
        such presentation and surrender.

               (g) Unless stated to the contrary on the face of any Note and in
        the applicable prospectus supplement or pricing supplement, a Note will
        not be subject to redemption prior to its Maturity Date. If stated on
        the face of a Note and in the applicable prospectus supplement or
        pricing supplement, such Note will be redeemable in whole or in part at
        the option of the Operating Partnership, in accordance with Article
        Eleven of the Indenture and the terms set forth in such Note and the
        applicable prospectus supplement or pricing supplement.


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               (h) Unless stated to the contrary on the face of any Note and in
        the applicable prospectus supplement or pricing supplement, such Note
        will not be subject to repayment prior to its Maturity Date. If stated
        on the face of a Note and in the applicable prospectus supplement or
        pricing supplement, such Note will be repayable by the Operating
        Partnership in whole or in part at the option of the Holder in
        accordance with the terms set forth in such Note and the applicable
        prospectus supplement or pricing supplement.

               (i) Unless stated to the contrary on the face of a Note and in
        the applicable prospectus supplement or pricing supplement, Notes shall
        be issuable in minimum denominations of (i) if the Notes are denominated
        in U.S. Dollars, $1,000 and in any larger amount in integral multiples
        of $1,000 and (ii) if the Notes are denominated in a currency other than
        U.S. Dollars (a "Foreign Currency") or in a composite currency, the
        equivalent in such Foreign Currency or composite currency determined in
        accordance with the Market Exchange Rate (as defined in the Notes) for
        such Foreign Currency or composite currency on the Business Day
        immediately preceding the date on which the Operating Partnership
        accepts an offer to purchase the Note, of $1000 (rounded to an integral
        multiple of 1,000 units of the Foreign Currency or composite currency),
        and in any larger amount in integral multiples of 1,000 units. The
        principal amount of any particular Note shall be determined by an
        officer of the Parent Guarantor, as general partner of the Operating
        Partnership, and specified to the Trustee in writing or by telephone
        (telephonic instructions to be promptly confirmed in writing).

               (j) Initially, unless otherwise stated to the contrary on the
        face of any Note and in the applicable prospectus supplement or pricing
        supplement, the Trustee shall be the registrar, transfer agent,
        authenticating agent, exchange rate agent, calculation agent and paying
        agent for the Notes. The Operating Partnership may from time to time
        name other or additional registrars, paying agents, authenticating
        agents, exchange rate agents, calculation agents or transfer agents.

               (k) Unless stated to the contrary on the face of a Note and in
        the applicable prospectus supplement or pricing supplement, such Note
        shall be issuable only in registered form without coupons in book-entry
        form, represented by one or more global notes recorded in the book-entry
        system maintained by The Depository Trust Company. If specified on the
        face thereof, Notes may be issued in certificated form issued to, and
        registered in the name of, the beneficial owner or its nominee.

               (l) The Notes are not convertible into any other security of the
        Operating Partnership or the Parent Guarantor. The Notes shall
        constitute senior unsecured and unsubordinated obligations of the
        Operating Partnership and will rank equally with all other unsecured and
        unsubordinated indebtedness of the Operating Partnership from time to
        time outstanding.

               (m) There are no restrictive covenants pertaining to the Notes
        other than those contained in the Indenture. Unless stated to the
        contrary on the face of any Note and in the applicable prospectus
        supplement or pricing supplement, the holders of the Notes shall have no
        special rights in addition to those provided in the Indenture upon the
        occurrence of any particular events. The Notes shall have no additional
        Events of Default in addition to the Events of Default set forth in
        Article Five of the Indenture.

               (n) The Notes will be unconditionally guaranteed on an unsecured
        basis by the Parent Guarantor and, if required by Section 1013 of the
        Indenture, the Subsidiary Guarantors.

        SECTION 102. FORM OF NOTES. The Notes shall be in the form of, and shall
have the terms set forth in, the specimens thereof attached hereto as Exhibits A
and B in fully registered fixed rate and


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floating rate form, respectively, with applicable blank terms completed and
additional terms added to reflect settlement and other specific information,
which terms shall be specified by an officer of the Parent Guarantor, as general
partner of the Operating Partnership to the Trustee in writing or by telephone
(telephonic instructions to be promptly confirmed in writing) and specified in
the applicable prospectus supplement or pricing supplement.

        SECTION 103. FORM OF SUBSIDIARY GUARANTEE. The form of the Subsidiary
Guarantee which shall be executed if required pursuant to Section 1013 of the
Indenture is attached hereto as Exhibit C.

        SECTION 104. FORM OF GUARANTEES. There are hereby authorized for
issuance by the Parent Guarantor Guarantees (as defined in the Indenture) of the
Notes, which Guarantees shall be in the form of, and shall have the terms set
forth in, the specimen of "Parent Guarantee" endorsed on the specimen Notes
attached hereto as Exhibits A and B.

        SECTION 105. PROCEDURES. The Trustee is hereby instructed to
authenticate and deliver from time to time the Notes, with Guarantees endorsed
thereon, pursuant to the following procedures:

            (a) the procedures set forth in the Administrative Procedures
attached as Exhibit B to the Distribution Agreement, as amended from time to
time; and

            (b) each advice of settlement information with respect to any of the
Notes issued pursuant to (a) above will be deemed an instruction by the
Operating Partnership and the Parent Guarantor to authenticate and deliver such
Notes and Guarantees.

                                   ARTICLE II
                                  MISCELLANEOUS

        SECTION 201. DEFINITIONS. Capitalized terms used but not defined in this
Fifth Supplemental Indenture shall have the meanings ascribed thereto in the
Indenture.

        SECTION 202. CONFIRMATION OF INDENTURE. The Indenture, as heretofore
supplemented and amended by this Fifth Supplemental Indenture, is in all
respects ratified and confirmed, and the Indenture, this Fifth Supplemental
Indenture and all indentures supplemental thereto shall be read, taken and
construed as one and the same instrument.

        SECTION 203. CONCERNING THE TRUSTEE. The Trustee assumes no duties,
responsibilities or liabilities by reason of this Fifth Supplemental Indenture
other than as set forth in the Indenture and, in carrying out its
responsibilities hereunder, shall have all of the rights, protections and
immunities which it possesses under the Indenture.

        SECTION 204. GOVERNING LAW. This Fifth Supplemental Indenture, the
Indenture and the Notes shall be governed by and construed in accordance with
the internal laws of the State of New York.

        SECTION 205. SEPARABILITY. In case any provision in this Fifth
Supplemental Indenture shall for any reason be held to be invalid, illegal or
unenforceable, the validity, legality and enforceability of the remaining
provisions shall not in any way be affected or impaired thereby.

        SECTION 206. COUNTERPARTS. This Fifth Supplemental Indenture may be
executed in any number of counterparts each of which shall be an original, but
such counterparts shall together constitute but one and the same instrument.


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        IN WITNESS WHEREOF, the parties hereto have caused this Fifth
Supplemental Indenture to be duly executed as of the day and year first above
written.

                                         AMB PROPERTY, L.P.

                                         By: AMB PROPERTY CORPORATION,
                                             as General Partner


                                         By: ___________________________________
                                             Name: _____________________________
                                             Title: ____________________________


                                         AMB PROPERTY CORPORATION


                                         By: ___________________________________
                                             Name: _____________________________
                                             Title: ____________________________


                                         STATE STREET BANK AND TRUST
                                         COMPANY OF CALIFORNIA, N.A., AS TRUSTEE


                                         By: ___________________________________
                                             Name: _____________________________
                                             Title: ____________________________

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                                                                       EXHIBIT A

                      FORM OF FIXED RATE MEDIUM-TERM NOTES




                                      A-1
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                                                                       EXHIBIT B

                     FORM OF FLOATING RATE MEDIUM-TERM NOTES


                                      B-1
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                                                                       EXHIBIT C

                              SUBSIDIARY GUARANTEE

        FOR VALUE RECEIVED, the undersigned hereby jointly and severally with
the Parent Guarantor pursuant to the Parent Guarantee and any other Subsidiary
Guarantors under their respective Subsidiary Guarantees, unconditionally
guarantees to the Holder of the accompanying Series B Medium-Term Note (the
"Note") issued by AMB Property, L.P. (the "Operating Partnership") under an
Indenture dated as of June 30, 1998 (together with the First Supplemental
Indenture, the Second Supplemental Indenture and the Third Supplemental
Indenture, each dated as of June 30, 1998, the Fourth Supplemental Indenture
dated as of August 15, 2000 and the Fifth Supplemental Indenture dated as of May
__, 2002, the "Indenture") among the Operating Partnership, AMB Property
Corporation, and State Street Bank and Trust Company of California, N.A., as
trustee (the "Trustee"), (a) the full and prompt payment of the principal of and
premium, if any, on such Note when and as the same shall become due and payable,
whether at the Maturity Date (as defined in the Note), by acceleration, by
redemption, repurchase or otherwise, and (b) the full and prompt payment of the
interest on such Note when and as the same shall become due and payable,
according to the terms of such Note and of the Indenture. In case of the failure
of the Operating Partnership punctually to pay any such principal, premium or
interest, the undersigned hereby agrees to cause any such payment to be made
punctually when and as the same shall become due and payable, whether at the
Maturity Date, upon acceleration, by redemption or repayment or otherwise, and
as if such payment were made by the Operating Partnership. The undersigned
hereby agrees, jointly and severally with the Parent Guarantor pursuant to the
Parent Guarantee and any other Subsidiary Guarantors under their respective
Subsidiary Guarantees, that its obligations hereunder shall be as principal and
not merely as surety, and shall be absolute and unconditional, and shall not be
affected, modified or impaired by the following: (a) the failure to give notice
to the Guarantors of the occurrence of an Event of Default under the Indenture;
(b) the waiver, surrender, compromise, settlement, release or termination of the
payment, performance or observance by the Operating Partnership or the
Guarantors of any or all of the obligations, covenants or agreements of any of
them contained in the Indenture or any Note; (c) the acceleration, extension or
any other changes in the time for payment of any principal of or interest or any
premium on any Note or for any other payment under the Indenture or of the time
for performance of any other obligations, covenants or agreements under or
arising out of the Indenture or any Note; (d) the modification or amendment
(whether material or otherwise) of any obligation, covenant or agreement set
forth in the Indenture or any Note; (e) the taking or the omission of any of the
actions referred to in the Indenture and in any of the actions under any Note;
(f) any failure, omission, delay or lack on the part of the Trustee to enforce,
assert or exercise any right, power or remedy conferred on the Trustee in the
Indenture, or any other action or acts on the part of the Trustee or any of the
Holders from time to time of any Note; (g) the voluntary or involuntary
liquidation, dissolution, sale or other disposition of all or substantially all
the assets, marshaling of assets and liabilities, receivership, insolvency,
bankruptcy, assignment for the benefit of creditors, reorganization,
arrangement, composition with creditors or readjustment of, or other similar
proceedings affecting the Guarantors or the Operating Partnership or any of the
assets of any of them, or any allegation or contest of the validity of this
Subsidiary Guarantee in any such proceeding; (h) to the extent permitted by law,
the release or discharge by operation of law of the Guarantors from the
performance or observance of any obligation, covenant or agreement contained in
the Indenture; (i) to the extent permitted by law, the release or discharge by
operation of law of the Operating Partnership from the performance or observance
of any obligation, covenant or agreement contained in the Indenture; (j) the
default or failure of the Operating Partnership Trustee fully to perform any of
its obligations set forth in the Indenture or any Note; (k) the invalidity,
irregularity or unenforceability of the Indenture or any Note or any part of any
thereof; (l) any judicial or governmental action affecting the Operating
Partnership or any Note or consent or indulgence granted to the Operating
Partnership by the Holders or by the Trustee; or (m) the recovery of any
judgment against the Operating Partnership or any action to enforce the same or
any other circumstance which might constitute a legal or equitable discharge of
a surety or guarantor. The undersigned hereby waives diligence, presentment,
demand of payment, filing of claims with a court in the event of merger, sale,
lease or conveyance of all or substantially all of its assets, insolvency or
bankruptcy of any Guarantor or the Operating Partnership, any right to require a
proceeding first against any other Guarantor or the Operating Partnership,
protest or notice with respect to such Note or the indebtedness evidenced
thereby and all demands whatsoever, and covenants that this Subsidiary Guarantee
will not be discharged except by complete performance of the obligations
contained in such Note and in this Subsidiary Guarantee.

        No reference herein to such Indenture and no provision of this
Subsidiary Guarantee or of such Indenture shall alter or impair the guarantee of
the undersigned, which is absolute and unconditional, of the full and prompt
payment of the principal of and premium, if any, and interest on the Note.

        THIS SUBSIDIARY GUARANTEE SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.


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        The validity and enforceability of this Subsidiary Guarantee shall not
be affected by the fact that it is not affixed to any particular Note.

        An Event of Default under the Indenture or any Note shall constitute an
event of default under this Subsidiary Guarantee, and shall entitle the Holder
of any Note to accelerate the obligations of the undersigned hereunder in the
same manner and to the same extent as the obligations of the Operating
Partnership.

        Notwithstanding any other provision of this Subsidiary Guarantee to the
contrary, the undersigned hereby waives any claims or other rights which it may
now have or hereafter acquire against any Guarantor or the Operating Partnership
that arise from the existence or performance of its obligations under this
Subsidiary Guarantee (all such claims and rights are referred to as "Guarantor's
Conditional Rights"), including, without limitation, any right of subrogation,
reimbursement, exoneration, contribution, or indemnification, any right to
participate in any claim or remedy against any Guarantor or the Operating
Partnership, whether or not such claim, remedy or right arises in equity or
under contract, statute or common law, by any payment made hereunder or
otherwise, including without limitation, the right to take or receive from any
Guarantor or the Operating Partnership, directly or indirectly, in cash or other
property or by setoff or in any other manner, payment or security on account of
such claim or other rights. The undersigned hereby agrees not to exercise any
rights which may be acquired by way of contribution under this Subsidiary
Guarantee or any other agreement, by any payment made hereunder or otherwise,
including, without limitation, the right to take or receive from any other
guarantor, directly or indirectly, in cash or other property or by setoff or in
any other manner, payment or security on account of such contribution rights.
If, notwithstanding the foregoing provisions, any amount shall be paid to the
undersigned party on account of any such Guarantor's Conditional Rights and
either (i) such amount is paid to such undersigned party at any time when the
indebtedness shall not have been paid or performed in full, or (ii) regardless
of when such amount is paid to the undersigned, any payment made by any
Guarantor or the Operating Partnership to a Holder that is at any time
determined to be a Preferential Payment (as defined below), then such amount
paid to the undersigned shall be held in trust for the benefit of the Holders
and shall forthwith be paid such Holder to be credited and applied upon the
indebtedness, whether matured or unmatured. Any such payment is herein referred
to as a "Preferential Payment" to the extent any Guarantor or the Operating
Partnership makes any payment to Holder in connection with the Note, and any or
all of such payment is subsequently invalidated, declared to be fraudulent or
preferential, set aside or required to be repaid or paid over to a trustee,
receiver or any other entity, whether under any bankruptcy act or otherwise.

        To the extent that any of the provisions of the immediately preceding
paragraph shall not be enforceable, the undersigned agrees that until such time
as the indebtedness has been paid and performed in full and the period of time
has expired during which any payment made by any Guarantor or the Operating
Partnership or the undersigned to a Holder may be determined to be a
Preferential Payment, Guarantor's Conditional Rights to the extent not validly
waived shall be subordinate to Holders' right to full payment and performance of
the indebtedness and the undersigned shall not enforce any of its respective
portion of the Guarantors' Conditional Rights until such time as the
indebtedness has been paid and performed in full and the period of time has
expired during which any payment made by any Guarantor or the Operating
Partnership or the undersigned to Holders may be determined to be a Preferential
Payment.

        The undersigned's liability (the "Base Guaranty Liability") shall be
that amount from time to time equal to the aggregate liability of the
undersigned hereunder, but shall be limited to the lesser of (A) the aggregate
amount of the obligation as stated in the second sentence of Section 1401 of the
Indenture, and (B) the amount, if any, which would not have (i) rendered the
undersigned "insolvent" (as such term is defined in Section 101(29) of the
Federal Bankruptcy Code and in Section 271 of the Debtor and Creditor Law of the
State of New York, as each is in effect at the date of the Indenture) or (ii)
left the undersigned with unreasonably small capital at the time this Subsidiary
Guarantee was entered into, after giving effect to the incurrence of existing
Debt (as defined in the Indenture) immediately prior to such time, provided
that, it shall be a presumption in any lawsuit or other proceeding in which the
undersigned is a party that the amount guaranteed is the amount set forth in (A)
above unless a creditor, or representative of creditors of the undersigned or a
trustee in bankruptcy of the undersigned, as debtor in possession, otherwise
proves in such a lawsuit that the aggregate liability of the undersigned is
limited to the amount set forth in (B). In making any determination as to the
solvency or sufficiency of capital of the undersigned in accordance with the
previous sentence, the right of the undersigned to contribution from the other
Guarantors, to subrogation and any other rights the undersigned may have,
contractual or otherwise, shall be taken into account.

        The obligations of the undersigned to the Holder of any Note and to the
Trustee pursuant to this Subsidiary Guarantee and the Indenture are expressly
set forth in Article 14 of the Indenture and reference is hereby made to the


                                      C-2
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Indenture for the precise terms of the Subsidiary Guarantee and all of the other
provisions of the Indenture to which this Subsidiary Guarantee relates.

        Capitalized terms in this Subsidiary Guarantee which are not defined
herein shall have the meanings assigned to them in the Indenture.

        IN WITNESS WHEREOF, the undersigned has caused this Subsidiary Guarantee
to be duly executed.

Dated: ____________________



                                             [NAME OF SUBSIDIARY]


                                             By: _______________________________


                                      C-3