Document:

<PAGE>

                                                                    Exhibit 10.8

                            FIRST AMENDMENT TO LEASE
                            ------------------------
                              (500 Sansome Street)

     THIS FIRST AMENDMENT TO LEASE ("Amendment") is made and entered into as of
the 31st day of May, 2000, by and between WXI/SAN REALTY, L.L.C., a Delaware
limited liability company ("Landlord"), and PLUMTREE SOFTWARE, INC., a
California corporation ("Tenant").

                                   RECITALS:
                                   --------

     A.   BPG Sansome, L.L.C., a Delaware limited liability company, as
predecessor-in-interest to Landlord and Tenant entered into that certain Office
Lease dated as of April 7, 1999 (the "Lease"), whereby Tenant leased certain
office space in the building located at 500 Sansome Street, San Francisco,
California.

     B.   By this Amendment, Landlord and Tenant desire to expand the Premises,
extend the Term and to otherwise modify the Lease as provided herein.

     C.   Unless otherwise defined herein, capitalized terms as used herein
shall have the same meanings as given thereto in the Lease.

     NOW, THEREFORE, in consideration of the foregoing recitals and the mutual
covenants contained herein, and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the, parties hereto
agree as follows:

                                  AGREEMENT:
                                  ---------

     1.   The Existing Premises. Landlord currently leases to Tenant that
          ---------------------
certain office space containing 16,551 rentable square feet located on the first
(1st) floor and mezzanine level of the Building and known as Suites M-4 and 100
(the "Existing Premises").

     2.   Expansion of the Premises. That certain space located on the first
          -------------------------
(1st), mezzanine and third (3rd) floors of the Building consisting of 15,840
rentable square feet, known as Suites 101 (2,651 rentable square feet), 102
(1,014 rentable square feet), M-100 (3,585 rentable square feet) and 310 (8,590
rentable square feet), as outlined on the floor plan attached hereto as
Exhibits. "A-1" through "A-3" and made a part hereof, is referred to herein as
the "Expansion Space." Tenant shall lease portions of the Expansion Space in
phases, effective as of the date ("Expansion Commencement Date") that is the
date Landlord tenders possession of the applicable portion of the Expansion
Space to Tenant. Accordingly, effective upon the Expansion Commencement Date for
a particular portion of the Expansion Space, the Existing Premises shall be
increased to include such portion of the Expansion Space. The addition of the
entire Expansion Space to the Existing Premises shall, effective as of the last
Expansion Commencement Date, increase the number of rentable square feet leased
by Tenant in the Building to a total of 32,391 rentable square feet. The
Expansion Commencement Date is anticipated to be July 1, 2000 as to Suite 101,
August 1, 2000 as to Suites M-100 and 102, and November 1, 2000 as to Suite 310;
however, Landlord will not be in default under the Lease if the applicable
Expansion Commencement Date does not occur by such dates. In the event that
Landlord has not delivered the applicable portion of the Expansion Space to
Tenant on or before the "Outside Date," which shall be one hundred eighty (180)
days after the anticipated date of delivery of such portion of the Expansion
Space, then the sole remedy of Tenant shall be the right to deliver a notice to
Landlord (the "Outside Date Termination Notice") electing to terminate this
Amendment as to that portion of the Expansion Space only (and monthly Base Rent
and Lessee's Percentage Share shall be adjusted accordingly and the Stated
Amount of the Letter of Credit shall be decreased by an amount equal to $61.75
multiplied by the number of rentable square feet terminated by Tenant),
effective upon receipt of the Outside Date Termination Notice by Landlord (the
"Effective Date"). Except as provided hereinbelow, the Outside Date Termination
Notice may be delivered by Tenant to Landlord, if at all, during the period from
the Outside Date through the date of delivery of the applicable portion of the
<PAGE>

Expansion Space to Tenant. Effective as of the Expansion Commencement Date for
the applicable portion of the Expansion Space, all references to the "Premises"
shall mean and refer to the Existing Premises as expanded by such portion of the
Expansion Space. Exhibit "A-4" attached hereto and made a part hereof depicts
the Existing Premises and the entire Expansion Space.

     3. Extended Lease Term. The Lease Expiration Date shall be extended such
        -------------------
that the Lease shall terminate on October 31, 2006 ("New Termination Date"). The
period from the applicable Expansion Commencement Date through the New
Termination Date is referred to herein as the "Extended Term."

     4. Monthly Base Rent. Notwithstanding the rates set forth in the Lease,
        -----------------
effective as of September 1, 2000, Tenant shall pay Monthly Base Rent for the
Existing Premises as set forth below. In addition, during the Extended Term,
Tenant shall pay Monthly Base Rent for the Expansion Space as follows:

<TABLE>
<CAPTION>
            Period of
            ---------                                                      Annual Base Rent Per
         Extended Term                     Monthly Base Rent               Rentable Square Foot
         -------------                     -----------------               --------------------
<S>                                   <C>                                  <C>
     Applicable Expansion             Existing Premises $73,100.25                       $53.00
     Commencement Date (or                    Suite 101 $11,708.58
     9/1/00 as to the Existing                Suite 102 $4,478.50
      Premises)--8/31/01 *                  Suite M-100 $15,833.75
                                              Suite 310 $37,939.17

      9/1/01--8/31/02                         $151,158.00                                $56.00
      9/1/02--8/31/03                         $161,955.00                                $60.00
      9/1/03--8/31/04                         $167,353.50                                $62.00
      9/1/04--8/31/05                         $172,752.00                                $64.00
      9/1/05--10/31/06                        $178,150.50                                $66.00
</TABLE>

*Subject to abatement as set forth in Section 4.4  of the Tenant Work Letter.

     5. Lessee's Percentage Share. Effective as of each applicable Expansion
        -------------------------
Commencement Date, Lessee's Percentage Share of any increase in Basic Costs for
the Premises shall be equal to a fraction, the numerator of which is the
rentable square footage of the Premises (as expanded by the applicable portion
of the Expansion Space), and the denominator of which is 147,470. Effective as
of the last Expansion Commencement Date, Lessee's Percentage Share of. any
increase in Basic Costs for the Premises shall be twenty-one point nine six
percent (21.96%).

     6. Tenant Improvements. Tenant Improvements in the Expansion Space shall be
        -------------------
installed and constructed in accordance with the terms of the Tenant Work Letter
attached hereto as Exhibit "B" and made a part hereof.

     7. Letter of Credit. Concurrently with Tenant's execution of this
        ----------------
Amendment, Tenant shall deliver to Landlord an unconditional, irrevocable and
renewable letter of credit ("Letter of Credit") in favor of Landlord in a form,
and issued by a federally insured bank, reasonably satisfactory to Landlord with
a branch located in San Francisco, in the principal amount ("Stated Amount")
specified below, as security for the faithful performance and observance by
Tenant of the terms, provisions and conditions of the Lease. Tenant shall pay
all expenses, points and/or fees incurred by Tenant in obtaining the Letter of
Credit. Within thirty (30) days after receipt of the Letter of Credit, Landlord
will return any unused portion of the Security Deposit posted by Tenant in
connection with the initial Lease. The Stated Amount shall initially be Two
Million Dollars ($2,000,000.00); provided, however, that upon the dates
specified below ("Adjustment Dates"), the Stated Amount may be reduced to the
following amounts:
<PAGE>

                      Month                 Stated Amount
                      -----                 -------------
                August 1, 2002              80% of the initial Stated Amount
                August 1, 2003              60% of the initial Stated Amount
                August 1, 2004              40% of the initial Stated Amount
                August 1, 2005              20% of the initial Stated Amount

     However, if (i) a default by Tenant occurs under the Lease and Tenant has
failed to cure such default within the time period permitted by Section 17.1 of
the Lease or such lesser time as may remain before the relevant Adjustment Date
as provided above, or (ii) a circumstance exists as of the relevant Adjustment
Date that would, with notice or lapse of time or both, constitute a default by
Tenant, then the Stated Amount shall not be reduced unless and until such
default shall have been fully cured pursuant to the terms of the Lease or such
circumstance ceases to exist, as applicable, at which time the Stated Amount may
be reduced as hereinabove described. The Letter of Credit shall state that an
authorized officer or other representative of Landlord may make demand on
Landlord's behalf for the Stated Amount of the Letter of Credit, or any portion
thereof, and that the issuing bank must immediately honor such demand, without
qualification or satisfaction of any conditions, except the proper
identification of the party making such demand. In addition, the Letter of
Credit shall indicate that it is transferable in its entirety by Landlord as
beneficiary and that upon receiving written notice of transfer, and upon
presentation to the issuing bank of the original Letter of Credit, the issuer or
confirming bank will reissue the Letter of Credit naming such transferee as the
beneficiary (Tenant shall pay to Landlord, within thirty (30) days following
written request therefor, any transfer fee payable in connection with such
transfer). The Letter of Credit will expire on November 30, 2006. If the term of
the Letter of Credit will expire prior to November 30, 2006, and it is not
extended, or a new Letter of Credit for an extended period of time is not
substituted, within thirty (30) days prior to the expiration of the Letter of
Credit, then Landlord shall be entitled to make demand for the Stated Amount of
said Letter of Credit and, thereafter, to hold such funds in accordance with
this Paragraph 7. The Letter of Credit and any such proceeds thereof shall be
held by Landlord as security for the faithful performance by Tenant of all of
the terms, covenants and conditions of the Lease. If Tenant commits a default
with respect to any provision of the Lease, Landlord may (but shall not be
required to) draw upon all or any portion of the Stated Amount of the Letter of
Credit, and Landlord may then use, apply or retain all or any part of the
proceeds for the payment of any sum which is in default, or for the payment of
any other amount which Landlord may spend or become obligated to spend by reason
of Tenant's default or to compensate Landlord for any loss or damage which
Landlord may suffer by reason of Tenant's default. If any portion of the Letter
of Credit proceeds are so used or applied, Tenant shall, within ten (10) days
after demand therefor, post an additional Letter of Credit in an amount to
cause the aggregate amount of the unused proceeds and such new Letter of Credit
to equal the Stated Amount required in this Paragraph 7 above. Landlord shall
not be required to keep any proceeds from the Letter of Credit separate from its
general funds. Should Landlord sell its interest in the Premises and if Landlord
deposits with the purchaser thereof the Letter of Credit or any proceeds of the
Letter of Credit, thereupon Landlord shall be discharged from any further
liability with respect to the Letter of Credit and said proceeds. Any remaining
proceeds of the Letter of Credit held by Landlord after expiration of the
Extended Term, after any deductions described in this Paragraph 7 above, shall
be returned to Tenant or, at Landlord's option, to the last assignee of Tenant's
interest hereunder, within thirty (30) days following the expiration of the
Extended Term.

     Notwithstanding anything to the contrary set forth above, in the event
Tenant provides Landlord with reasonably satisfactory proof that the following
conditions have been satisfied, Tenant shall have the right to decrease the
Letter of Credit to an amount equal to $178,156.00 (or, at Tenant's option, to
substitute the equivalent amount of cash in lieu of the Letter of Credit)
effective as of the date the following conditions are satisfied: (i) Tenant
provides such reasonably satisfactory proof to Landlord that Tenant's shares are
traded on a public stock exchange of the United States; (ii) Tenant provides
Landlord with quarterly financial statements for the most recent three (3)
consecutive quarters prepared in accordance with generally accepted accounting
principles, each showing that Tenant has sustained a positive net profit over
such period; (iii) Tenant provides such reasonably satisfactory proof to
Landlord that Tenant's net worth, calculated in accordance with generally
accepted accounting principles, is in excess of Fifty Million Dollars
($50,000,000.00); and (iv) no default by Tenant under the Lease exists and
<PAGE>

no circumstance exists that would, with notice or lapse of time, or both,
constitute a default by Tenant.

     8. Addresses for Notice. Section 3 of the Summary of Basic Lease
        --------------------
Information is hereby amended to provide that notices to Landlord shall be
delivered to Landlord c/o WCB Properties, 450 Newport Center Drive, Suite 304,
Newport Beach, California 92660, Attention: Mr. Ronald A. Lack. In addition,
Section 5 of the Summary of Basic Lease Information is hereby amended to provide
that notices to Tenant shall be delivered to the address set forth in Section 5
of the Lease, with a copy to Mr. Steve Anderson, The CAC Group, Inc., 255
California Street, San Francisco, California 94111.

     9. Option to Extend. Landlord hereby grants to the original Tenant named in
        ----------------
this Amendment (the "Original Tenant"), one (1) option to extend the Extended
Term for a period of five (5) years (an "Option Term"), which option shall be
exercisable only by written notice ("Option Notice") delivered by Tenant to
Landlord as provided in Section 9(b) below, provided that, as of the date of
delivery of such notice and, at Landlord's option, as of the last day of the
Extended Term, Tenant is not in default under the Lease after expiration of
applicable cure periods. The right contained in this Section 9 shall be personal
to the Original Tenant and may only be exercised by the Original Tenant (and not
any assignee, sublessee or other transferee of the Original Tenant's interest in
the Lease) if the Original Tenant occupies the entire Existing Premises and
Expansion Space as of the date of the Option Notice.

        (a) Option Rent. The Rent payable by Tenant during the Option Term (the
            -----------
"Option Rent") shall be equal to the fair market rent for the Premises as of the
commencement date of the Option Term, but in no event less than the amount
Tenant is paying immediately prior to the Option Term. The fair market rent
shall be the rental rate, including all escalations, at which tenants, as of the
commencement of the Option Term, are leasing non-sublease, non-encumbered space
comparable in size, location and quality to the Premises for a term of five (5)
years, which comparable space is located in other first-class, high-rise office
buildings in the vicinity of the Building in San Francisco, California.

        (b) Exercise of Option. The option contained in this Section 9 shall be
            ------------------
exercised by Tenant, if at all, only in the following manner: (i) Tenant shall
deliver written notice ("Interest Notice") to Landlord on or before the date
which is twelve (12) months prior to the expiration of the Extended Term,
stating that Tenant is interested in exercising its option; (ii) Landlord,
within thirty (30) days after receipt of the Interest Notice, shall deliver
notice (the "Option Rent Notice") to Tenant setting forth Landlord's reasonable,
good-faith determination of the Option Rent; and (iii) if Tenant wishes to
exercise such option, Tenant shall, within thirty (30) days after Tenant's
receipt of the Option Rent Notice, exercise the option by delivering written
notice (the "Option Notice") to Landlord and upon, and concurrent with, such
exercise, Tenant may, at its option, object to the Option Rent determined by
Landlord. If Tenant exercises the option to extend but objects to the Option
Rent contained in the Option Rent Notice, then the Option Rent shall be
determined as set forth in Section 9(c) below. In the event Landlord fails to
deliver the Option Rent Notice within the thirty (30) day period set forth
above, Tenant may provide a notice to Landlord setting forth such failure, and
in the event Landlord fails to deliver the Option Rent Notice to Tenant within
twenty (20) days after receipt of such notice from Tenant, Tenant may invoke the
arbitration provision set forth in Section 9(c) below, by providing written
notice of such election to Landlord. Failure of Tenant to deliver the Interest
Notice to Landlord on or before the date specified in (i) above or to deliver
the Option Notice to Landlord on or before the date specified in (iii) above
shall be deemed to constitute Tenant's failure to exercise its option to extend.
If Tenant timely and properly exercises its option to extend, the Extended Term
shall be extended for the Option Term upon all of the terms and conditions set
forth in the Lease, except that the Base Rent shall be as indicated in the
Option Rent Notice or determined in accordance with Section 9(c) below, and all
references in the Lease to the Term shall include the Option Term.

        (c) Determination of Option Rent. In the event Tenant exercises its
            ----------------------------
option to extend but objects to Landlord's determination of the Option Rent
concurrently with its exercise of the option to extend, Landlord and Tenant
shall attempt to agree in good faith upon the Option Rent. If Landlord and
Tenant fail to reach agreement within twenty (20) days following Tenant's
delivery of the Option Notice (the "Outside Agreement Date"), or if Landlord
fails to deliver the Option Rent Notice within the time periods set forth above
and Tenant so elects, then Tenant shall make a determination of the Option Rent,
within five (5) business days after the Outside Agreement Date (or the receipt
of notice from Tenant of its election to submit to arbitration), and
<PAGE>

Landlord shall use the rental rate set forth in the Option Rent Notice. Tenant
shall provide Landlord with a copy of its determination and each party's
determination shall be submitted to arbitration in accordance with Sections
9(c)(l) through 9(c)(7) below.

        (1) Landlord and Tenant shall each appoint one arbitrator who shall by
profession be a real estate broker or appraiser who shall have been active over
the five (5) year period ending on the date of such appointment in the leasing
(or appraisal, as the case may be) of first-class commercial properties in the
vicinity of the Building in San Francisco, California. The determination of the
arbitrators shall be limited solely to the issue of whether Landlord's or
Tenant's submitted Option Rent is the closest to the actual Option Rent, as
determined by the arbitrators, taking into account the requirements of Section
9(a) above. Each such arbitrator shall be appointed within fifteen (15) business
days after the applicable Outside Agreement Date.

        (2) The two (2) arbitrators so appointed shall within five (5) days of
the date of the appointment of the last appointed arbitrator agree upon and
appoint a third arbitrator who shall be qualified under the same criteria set
forth hereinabove for qualification of the initial two (2) arbitrators.

        (3) The three (3) arbitrators shall within five (5) days of the
appointment of the third arbitrator reach a decision as to whether the parties
shall use Landlord's or Tenant's submitted Option Rent and shall notify Landlord
and Tenant thereof.

        (4) The decision of the majority of the three (3) arbitrators shall be
binding upon Landlord and Tenant.

        (5) If either Landlord or Tenant fails to appoint an arbitrator within
fifteen (15) business days after the applicable Outside Agreement Date, the
arbitrator appointed by one of them shall reach a decision, notify Landlord and
Tenant thereof, and such arbitrator's decision shall be binding upon Landlord
and Tenant.

        (6) If the two (2) arbitrators fail to agree upon and appoint a third
arbitrator, or both parties fail to appoint an arbitrator, then the appointment
of the third arbitrator or any arbitrator shall be dismissed and the Option Rent
to be decided shall be forthwith submitted to arbitration under the provisions
of the American Arbitration Association, but subject to the instruction set
forth in this Section 9(c).

        (7) The cost of arbitration shall be paid by the losing party.

     10. Right of First Offer. Landlord hereby grants to Tenant a one-time right
         --------------------
of first offer with respect to that space on the second (2nd) floor of the
Building and known as Suite 200, as outlined on Exhibit "A-5" attached hereto
and made a part hereof ("First Offer Space"). Tenant's first offer right shall
only apply in the event the tenant under the existing lease for the First Offer
Space (the "Superior Lease") does not renew or extend the Superior Lease
pursuant to, or substantially in accordance with, the option to extend granted
pursuant to such existing lease (provided that a change in the term of such
existing tenant's extension option shall be "substantially in accordance" with
the terms of such option to extend for purposes of this Amendment as long as the
term is at least three (3) years), and Tenant's first offer right shall be
subordinate and secondary to all rights of expansion, first refusal, first offer
or similar rights granted to any other tenant of the Building prior to the date
hereof (the rights described above to be known collectively as "Superior
Rights"). If the tenant under the Superior Lease does so renew or extend the
Superior Lease, the provisions of this Section 10 shall be null and void.
Tenant's right of first offer shall be on the terms and conditions set forth in
this Section 10.

        (a) Procedure for Offer. Landlord shall notify Tenant (the "First Offer
            -------------------
Notice") when Landlord determines that Landlord shall commence the marketing of
all or any portion of the First Offer Space because such space shall become
available for lease to third parties, where no holder of a Superior Right
desires to lease such space. The First Offer Notice shall describe the space so
offered to Tenant and shall set forth Landlord's proposed economic terms and
conditions applicable to Tenant's lease of such space, provided that the term
for such lease shall be coterminous with the Extended Term (collectively, the
"Economic Terms"). The Economic Terms shall include Landlord's proposed rental
rate for the First Offer Space, which shall be Landlord's good faith
determination of the fair market rental rate for such First Offer Space, taking
into consideration rates being paid by tenants of similar credit-worthiness, in
nonsublease, non-encumbered transactions for a comparable term, with space of
similar size and
<PAGE>

quality as the First Offer Space, which comparable space is located in the
Building or in other first-class buildings in the vicinity of the Building in
San Francisco, California.

         (b) Procedure for Acceptance. If Tenant wishes to exercise Tenant's
             ------------------------
right of first offer with respect to the space described in the First Offer
Notice, then within five (5) business days after delivery of the First Offer
Notice to Tenant, Tenant shall deliver notice to Landlord of Tenant's intention
to exercise its right of first offer with respect to the entire space described
in the First Offer Notice. If concurrently with Tenant's exercise of the first
offer right, Tenant notifies Landlord that it does not accept the Economic Terms
set forth in the First Offer Notice, Landlord and Tenant shall, for a period of
fifteen (15) days after Tenant's exercise, negotiate in good faith to reach
agreement as to such Economic Terms. If Tenant does not so notify Landlord that
it does not accept the Economic Terms set forth in the First Offer Notice
concurrently with Tenant's exercise of the first offer right, the Economic Terms
shall be as set forth in the First Offer Notice. In addition, if Tenant does not
exercise its right of first offer within the five (5) business day period, or,
if Tenant exercises its first offer right but timely objects to Landlord's
determination of the Economic Terms and if Landlord and Tenant are unable to
reach agreement on such Economic Terms within said fifteen (15) day period, then
Landlord shall be free to lease the space described in the First Offer Notice to
anyone to whom Landlord desires on any terms Landlord desires and Tenant's right
of first offer shall terminate as to the First Offer Space described in the
First Offer Notice. Notwithstanding anything to the contrary contained herein,
Tenant must elect to exercise its right of first offer, if at all, with respect
to all of the space offered by Landlord to Tenant at any particular time, and
Tenant may not elect to lease only a portion thereof. In the event Tenant
exercises its right of first offer pursuant to the terms of this Section 10, the
parties shall execute an amendment adding the First Offer Space to the Premises
and all terms and conditions of the Lease shall apply to the First Offer Space,
except to the extent inconsistent with the Economic Terms. In addition, in the
event the First Offer Space is added to the Premises, Tenant shall increase the
Stated Amount of the Letter of Credit required to be maintained by Tenant
pursuant to Section 7 above (or post an additional Letter of Credit, subject to
all terms and conditions of Section 7 above) by (or in) an amount equal to
$61.75 multiplied by the number of rentable square feet in the First Offer
Space.

     11. Insurance. The combined single limit of the insurance required to be
         ---------
carried pursuant to Section 9.2(b) of the Lease shall, effective as of August 1,
2000, be increased to Two Million Dollars ($2,000,000.00) per occurrence and
Three Million Dollars ($3,000,000.00) in the aggregate.

     12. Notice of Lease Term Dates. Landlord shall deliver to Tenant a
         --------------------------
commencement letter(s) confirming the Expansion Commencement Dates. Tenant
agrees to execute and return to Landlord said commencement letter(s) within five
(5) days after Tenant's receipt thereof.

     13. Transfer Premium. In the first sentence of Section 13.4 of the Lease,
         ----------------
the reference to fifty percent (50%) is hereby replaced with seventy percent
(70%).

     14. Relocation Right. Notwithstanding anything to the contrary set forth in
         ----------------
the Lease, the relocation right set forth in Section 20.21 of the Lease shall
not apply to any full floor(s) leased by Tenant in the Building.

     15. Brokers. Each party represents and warrants to the other that no
         -------
broker, agent or finder negotiated or was instrumental in negotiating or
consummating this Amendment, other than Cushman & Wakefield and the CAC Group
(collectively, the "Brokers"). Each party further agrees to defend, indemnify
and hold harmless the other party from and against any claim for commission or
finder's fee by any person or entity who claims or alleges that they were
retained or engaged by the indemnifying party or at the request of such party in
connection with this Amendment. The Brokers shall be compensated by Landlord
pursuant to a separate agreement.

     16. Signing Authority. Each individual executing this Amendment on behalf
         -----------------
of Landlord and Tenant represents that such individual is authorized to do so.

     17. Defaults. Tenant hereby represents and warrants to Landlord that, as of
         --------
the date of this Amendment, Tenant is in full compliance with all terms,
covenants and conditions of the Lease and that there are no breaches or defaults
under the Lease by Landlord or Tenant, and

                                      -6-
<PAGE>

that Tenant knows of no events or circumstances which, given the passage of
time, would constitute a default under the Lease by either Landlord or Tenant.

     18. No Further Modification. Except as set forth in this Amendment, all of
         -----------------------
the terms and provisions of the Lease shall apply with respect to the Expansion
Space and shall remain unmodified and in full force and effect. Effective as of
the date hereof, all references to the "Lease" shall refer to the Lease as
amended by this Amendment.

     IN WITNESS WHEREOF, this Amendment has been executed as of the day and year
first above written.

                                     "Landlord":

                                     WXI/SAN REALTY, L.L.C.,
                                     a Delaware limited liability company

                                     By: MRC Properties VI, L.L.C.,
                                         a Delaware limited liability company

                                         By:    [Signature Illegible]
                                               -------------------------------
                                               Its: VICE PRESIDENT
                                                   ---------------------------

                                     "Tenant":

                                     PLUMTREE SOFTWARE, INC.,
                                     a California corporation

                                     *By: /s/ John Kunze
                                          ------------------------------------
                                      Print Name: John Kunze
                                                 -----------------------------
                                           Title: CEO
                                                 -----------------------------

                                     *By: /s/ Peter F. Seidenberg
                                          ------------------------------------
                                      Print Name: Peter F. Seidenberg
                                                 -----------------------------
                                           Title: Dir. of Finance
                                                 -----------------------------

-----------------------------
* NOTE:
One of the following alternative requirements must be satisfied:
(A) This Amendment must be signed by two (2) officers of such corporation: one
being the chairman of the board, the president or a vice president, and the
other being the secretary, an assistant secretary, the chief financial officer
or an assistant treasurer.
(B) If there is only one (1) signatory, or if the two (2) signatories do not
satisfy the requirements of (A) above, then Tenant shall deliver to Landlord a
certified copy of a corporate resolution in a form reasonably acceptable to
Landlord authorizing the signatory(ies) to execute this Amendment.

                                      -7-
<PAGE>

                                  EXHIBIT A-1
                                  -----------

                      EXPANSION SPACE--Suites 101 and 102

                        [GRAPHICAL INFORMATION OMITTED]

                                  EXHIBIT A-1
                                      -1-

<PAGE>

                                  EXHIBIT A-2
                                  -----------

                         EXPANSION SPACE--Suite M-100

                        [GRAPHICAL INFORMATION OMITTED]

                                  EXHIBIT A-2
                                      -1-

<PAGE>

                                  EXHIBIT A-3
                                  -----------

                          EXPANSION SPACE--Suite 310

                        [GRAPHICAL INFORMATION OMITTED]

                                  EXHIBIT A-3
                                      -1-

<PAGE>

                                  EXHIBIT A-4
                                  -----------

                 ENTIRE EXPANSION SPACE AND EXISTING PREMISES

                        [GRAPHICAL INFORMATION OMITTED]

                                  EXHIBIT A-4
                                      -1-

<PAGE>

                        [GRAPHICAL INFORMATION OMITTED]

                                  EXHIBIT A-4
                                      -2-

<PAGE>

                        [GRAPHICAL INFORMATION OMITTED]

                                  EXHIBIT A-4
                                      -3-

<PAGE>

                                  EXHIBIT A-5
                                  -----------

                               FIRST OFFER SPACE

                        [GRAPHICAL INFORMATION OMITTED]

                                  EXHIBIT A-5
                                      -1-

<PAGE>

                                    EXHIBIT B
                                    ---------

                               TENANT WORK LETTER
                               ------------------

     This Tenant Work Letter shall set forth the terms and conditions relating
to the construction of the Expansion Space. This Tenant Work Letter is
essentially organized chronologically and addresses the issues of the
construction of the Expansion Space, in sequence, as such issues will arise
during the actual construction of the Expansion Space. All references in this
Tenant Work Letter to Articles or Sections of "the Lease" shall mean the
relevant portions of the Lease, as amended by the Amendment to which this Tenant
Work Letter is attached, and all references in this Tenant Work Letter to
Sections of "this Tenant Work Letter" shall mean the relevant portions of this
Tenant Work Letter.

                                    SECTION 1

             LANDLORD'S INITIAL CONSTRUCTION IN THE EXPANSION SPACE
             ------------------------------------------------------

     Landlord has constructed, at its sole cost and expense, the base, shell,
and core (i) of the Expansion Space and (ii) of the floors of the Building on
which the Expansion Space is located (collectively, the "Base, Shell, and
Core"). In addition, leasehold improvements to the Expansion Space may have been
constructed for a previous tenant. Tenant acknowledges that the Base, Shell and
Core and any such leasehold improvements shall be provided in their existing "as
is" condition. Any renovations to the existing leasehold improvements shall be
designed and constructed pursuant to this Tenant Work Letter, and the cost of
designing and constructing such renovations shall be Construction Costs.

                                    SECTION 2

                                  IMPROVEMENTS
                                  ------------

     2.1 Improvement Allowance. Tenant shall be entitled to a one-time tenant
         ---------------------
improvement allowance (the "Improvement Allowance") in the amount of $151,700
(based upon $15.00 per rentable square foot of Suite M-100, 101 and 102, and
$5.00 per rentable square foot of Suite 310) for the costs relating to the
initial design and construction of Tenant's improvements, which are permanently
affixed to the Expansion Space (the "Improvements"). Tenant may use the
Improvement Allowance in any space leased by Tenant in the Building, and the
allocation of specific amounts to specific Suites is for measurement purposes
only. In no event shall Landlord be obligated to make disbursements pursuant to
this Tenant Work Letter in a total amount which exceeds the Improvement
Allowance. The Improvement Allowance may be used by Tenant at any time prior to
the date which is six (6) months after the last Expansion Commencement Date
pursuant to this Amendment. All Improvements for which the Improvement Allowance
has been made available shall be deemed Landlord's property under the terms of
the Lease. Tenant shall not be entitled to any credit for any unused portion of
the Improvement Allowance.

     Notwithstanding anything to the contrary in the Lease or this Work Letter,
the Improvements for Suites 101, 102 and M-100 shall provide for an open
mezzanine to the first floor that is substantially similar to and consistent
with the mezzanine in the Existing Premises, and the Construction Costs shall
include the cost of any changes to the Base, Shell and Core that are necessary
in order to accommodate such mezzanine ("Necessary Mezzanine Changes"); however,
the foregoing shall not require Tenant to construct any particular number of
offices on the mezzanine.

     2.2 Disbursement of the Improvement Allowance. Except as otherwise set
         -----------------------------------------
forth in this Tenant Work Letter, the Improvement Allowance shall be disbursed
by Landlord (each of which disbursements shall be made pursuant to Landlord's
disbursement process), only for the following items and costs (collectively, the
"Construction Costs"):

         2.2.1 Payment of the fees of the "Architect" and the "Engineers," as
those terms are defined in Section 3.1 of this Tenant Work Letter, and payment
of the fees incurred by, and the cost of documents and materials supplied by,
Landlord and Landlord's consultants in connection with the preparation and
review of the "Construction Drawings," as that term is defined in Section 3.1.
of this Tenant Work Letter;

                                   EXHIBIT B
                                      -1-
<PAGE>

         2.2.2 The payment of plan check, permit and license fees relating to
construction of the Improvements;

         2.2.3 The cost of construction of the Improvements;

         2.2.4 The cost of any changes in the Base, Shell and Core when such
changes are required by the Construction Drawings (including if such changes are
due to the fact that such work is prepared on an unoccupied basis) and are due
to Tenant's particular use (i.e., to the extent Tenant's use of the Premises is
different from usual and customary office use) or are otherwise required by law
as a result of the construction of the Improvements, such cost to include all
direct architectural and/or engineering fees and expenses incurred in connection
therewith;

         2.2.5 The cost of any changes to the Construction Drawings or
Improvements required by applicable building code or any other governmental law
or regulation (collectively, "Code");

         2.2.6 Sales and use taxes;

         2.2.7 "Landlord's Supervision Fee," as that term is defined in Section
4.3.2 of this Tenant Work Letter; and

         2.2.8 All other reasonable costs to be expended by Landlord or Tenant
in connection with the construction of the Improvements.

     2.3 Standard Improvement Package. The Improvements to be constructed in
         ----------------------------
accordance with this Tenant Work Letter will be constructed using materials and
finishes which are comparable to the materials and finishes customarily used in
first-class office buildings in the San Francisco area. Tenant shall utilize
materials and finishes which are not of lesser quality than the materials and
finished found in comparable buildings in the vicinity of the Building.

                                    SECTION 3

                              CONSTRUCTION DRAWINGS
                              ---------------------

     3.1 Selection of Architect/Construction Drawings. Landlord shall retain
         --------------------------------------------
Huntsman Architecture Group (the "Architect") to prepare the "Construction
Drawings," as that term is defined in this Section 3.1. Landlord shall also
retain Landlord's designated engineering consultants (the "Engineers") to
prepare all plans and engineering working drawings relating to the structural,
mechanical, electrical, plumbing, HVAC, lifesafety, and sprinkler work in the
Expansion Space. Landlord shall ensure that the Engineers charge rates which are
comparable to the rates charged by similarly qualified engineers performing
similar work in comparable buildings in the vicinity of the Building. The plans
and drawings to be prepared by the Architect and the Engineers hereunder shall
be known collectively as the "Construction Drawings." Notwithstanding that
Landlord has retained the Architect and Engineers to prepare the Construction
Drawings, Landlord shall have no liability whatsoever in connection therewith
and shall not be responsible for any omissions or errors contained in the
Construction Drawings.

     3.2 Final Space Plan. Tenant and the Architect shall prepare the final
         ----------------
space plan for Improvements in the Expansion Space (collectively, the "Final
Space Plan"), which Final Space Plan shall include a layout and designation of
all offices, rooms and other partitioning, their intended use, and equipment to
be contained therein, and Tenant shall "sign-off' on such Final Space Plan to
evidence its approval of the Final Space Plan. The Final Space Plan will be
prepared and signed by Tenant on or before November 1, 2000, and any delay in
completing the Final Space Plan beyond such date shall be a Tenant Delay
pursuant to Section 5 below. After Tenant approves the Final Space Plan, Tenant
shall deliver the Final Space Plan to Landlord for Landlord's approval or
reasonable disapproval, which approval or reasonable disapproval shall be
delivered by Landlord to Tenant no later than five (5) days after Landlord's
receipt of such Final Space Plan. If Landlord reasonably disapproves of any
portion of the Final Space Plan, the parties shall meet, within five (5) days
after Landlord's disapproval, to agree upon revisions to be made to the Final
Space Plan to meet the reasonable satisfaction of Landlord. The Architect shall
then revise the Final Space Plan to the form agreed upon in such meeting and
Landlord shall then approve or reasonably disapprove the revised Final Space
Plan no later than two (2) days after Landlord's receipt of such revised Final
Space Plan. If Landlord shall again reasonably disapprove the revised Final
Space Plan, the parties will revise and review

                                    EXHIBIT B
                                       -2-
<PAGE>

Space Plan again in accordance with the procedure set forth above until
Landlord's reasonable approval is obtained.

     3.3 Final Working Drawings. Landlord, the Architect and the Engineers shall
         ----------------------
complete the architectural and engineering drawings for the Expansion Space, and
the Architect shall compile a fully coordinated set of architectural,
structural, mechanical, electrical and plumbing working drawings in a form which
is complete to allow subcontractors to bid on the work and to obtain all
applicable permits (collectively, the "Final Working Drawings") and shall submit
the same to Tenant for Tenant's approval or reasonable disapproval, which
approval or reasonable disapproval shall be delivered by Tenant to Landlord no
later than five (5) days after Tenant's receipt of such Final Working Drawings.
If Tenant reasonably disapproves of any portion of the Final Working Drawings,
the parties shall meet, within five (5) days after Tenant's disapproval, to
agree upon revisions to be made to the Final Working Drawings to meet the
reasonable satisfaction of Tenant. The Architect shall then revise the Final
Working Drawings to the form agreed upon in such meeting. Tenant shall then
approve the revised Final Working Drawings no later than two (2) days after
Tenant's receipt of such revised Final Working Drawings. If Tenant shall again
reasonably disapprove the revised Final Working Drawings, the parties will
revise and review the Final Working Drawings again in accordance with the
procedure set forth above until Tenant's reasonable approval is obtained. The
Final Working Drawings, as approved by Tenant, may be referred to herein as the
"Approved Working Drawings."

     3.4 Approved Working Drawings. Landlord shall submit the Approved Working
         -------------------------
Drawings to the appropriate governmental entities for all applicable building
permits necessary to allow "Contractor," as that term is defined in Section 4.1
of this Tenant Work Letter, to commence and fully complete the construction of
the Improvements (the "Permits"). If Tenant desires any change, modification or
alteration in the Approved Working Drawings, Tenant must first obtain the
reasonable prior written consent of Landlord, provided that in the event such
change will directly or indirectly delay the Substantial Completion of the
Expansion Space, such change will be a Tenant Delay pursuant to Section 5.2.5
below and further provided that Landlord may not refuse to consent to such
change order solely on the basis that such change order will increase the cost
of the Improvements. Prior to commencing any change requested by Tenant to the
Approved Working Drawings, Landlord shall prepare and deliver to Tenant, for
Tenant's approval, a change order ("Change Order") setting forth the additional
time required to perform the change and the total cost of such change, which
shall include associated architectural, engineering and Contractor's fees. If
Tenant fails to approve such Change Order in writing within two (2) business
days after such delivery by Landlord, Tenant shall be deemed to have withdrawn
the Change Order and Landlord shall not proceed to perform the change.

     3.5 Time Deadlines. Landlord and Tenant shall cooperate with (i) the
         --------------
Architect, the Engineers, and one another to complete all phases of the
Construction Drawings and the permitting process, and (ii) the Contractor, for
approval of the "Cost Proposal," as that term is defined in Section 4.2, below,
in accordance with the dates set forth herein. Landlord and Tenant shall meet on
a weekly basis to discuss their progress in connection with the same. The
applicable dates for approval of items, plans and drawings and selection of a
contractor as described in this Tenant Work Letter are referred to herein as the
"Time Deadlines." Landlord and Tenant agree to comply with the Time Deadlines.

                                    SECTION 4

                     CONSTRUCTION OF THE TENANT IMPROVEMENTS
                     ---------------------------------------

     4.1 Contractor. The contractor which shall construct the Improvements shall
         ----------
be a contractor selected pursuant to the following procedure. The Final Working
Drawings shall be submitted by Landlord to two (2) general contractors selected
by Landlord, provided that Landlord will endeavor to bid to three (3)
contractors, depending upon availability of qualified and acceptable contractors
capable of performing the work in accordance with Landlord's time schedule.
Landlord will give Tenant written notice of the names of the contractors
selected by Landlord and Tenant shall have the right to reasonably disapprove
any of the contractors by giving Landlord written notice thereof within two (2)
days following Tenant's receipt of the names of such contractors, which notice
shall specify the reasons for Tenant's disapproval (Tenant's failure to give
such disapproval notice to Landlord with such two (2) day period shall
constitute Tenant's approval of the contractors). Each such contractor shall be
invited to submit a sealed, fixed price contract bid (on such bid form as
Landlord shall designate) to construct the

                                    EXHIBIT B
                                       -3-
<PAGE>

Improvements. Each contractor shall be notified in the bid package of the time
schedule for construction of the Improvements. The contractors will be required
to competitively bid all subtrades. Tenant shall be entitled to review the bids
received by Landlord. The bids shall be submitted promptly to Landlord and a
reconciliation shall be performed by Landlord to adjust inconsistent or
incorrect assumptions so that a like-kind comparison can be made and a low
bidder determined. Landlord shall select the contractor who shall be the lowest
bidder and who states that it will be able to meet Landlord's construction
schedule. The contractor selected may be referred to herein as the "Contractor".
Landlord shall cause the Improvements to be constructed in accordance with the
Approved Working Drawings and no changes shall be made without Tenant's consent
(unless such changes are required by a building inspector or another
governmental authority or legal requirement).

     4.2 Cost Proposal. After the Approved Working Drawings are approved by
         -------------
Landlord and Tenant, Landlord shall provide Tenant with a cost proposal in
accordance with the Approved Working Drawings, which cost proposal shall
include, as nearly as possible, the cost of all items necessary to construct the
Improvements including both hard and soft costs and the Landlord Supervision
Fee, including any amounts already disbursed by Landlord or in the process of
being disbursed by Landlord (the "Cost Proposal"). Landlord does not guaranty
the accuracy of the Cost Proposal. Notwithstanding the foregoing, portions of
the cost of the Improvements may be delivered to Tenant as such portions of the
Improvements are priced by Contractor (on an individual item-by-item or
trade-by-trade basis), even before the Approved Working Drawings are completed
(the "Partial Cost Proposal"). Tenant shall either (i) approve and deliver the
Cost Proposal to Landlord within five (5) business days of the receipt of the
same (or, as to a Partial Cost Proposal, within three (3) business days of
receipt of the same), or (ii) notify Landlord within five (5) business days
after Tenant's receipt of the Cost Proposal (or Partial Cost Proposal, as the
case may be) that Tenant desires to revise the Approved Working Drawings to
reduce the amount of the Cost Proposal (or Partial Cost Proposal, as the case
may be), in which case such changes shall be made to the Approved Working
Drawings only in accordance with Section 3.4 above and the revised Working
Drawings shall be provided to the Contractor for repricing whereupon Landlord
shall revise the Cost Proposal (or Partial Cost Proposal, as the case may be)
for Tenant's approval. This procedure shall be repeated until the Cost Proposal
(or Partial Cost Proposal, as the case may be) is approved by Tenant. The date
by which Tenant has approved the Cost Proposal, or the last Partial Cost
Proposal, as the case may be, shall be known hereafter as the "Cost Proposal
Delivery Date." The total of all Partial Cost Proposals, if any, shall be known
as the Cost Proposal. All costs expended in connection with the construction of
the Improvements shall be submitted to Tenant for approval in accordance with
this Section 4.2.

     4.3 Construction of Improvements by Landlord's Contractor under the
         ---------------------------------------------------------------
Supervision of Landlord.
-----------------------

         4.3.1 Over-Allowance Amount. On the Cost Proposal Delivery Date,
               ---------------------
Tenant shall deliver to Landlord cash in an amount (the "Over-Allowance
Amount") equal to the difference between (i) the amount of the Cost Proposal and
(ii) the amount of the Improvement Allowance. The Over-Allowance Amount shall be
disbursed by Landlord after disbursement of the Improvement Allowance. In the
event that after the Cost Proposal Date, any revisions, changes, or
substitutions shall be made to the Construction Drawings or the Improvements,
any additional costs which arise in connection with such revisions, changes or
substitutions shall be paid by Tenant to Landlord immediately upon Landlord's
request as an addition to the Over-Allowance Amount. In addition, upon
Landlord's determination of the actual costs incurred by or on behalf of
Landlord for the Construction Costs, Tenant shall pay Landlord the amount, if
any, by which such actual costs exceed the sum of the Improvement Allowance and
the Over-Allowance Amount within fifteen (15) days after being billed therefor,
or Landlord may, at its election, require that Tenant deposit with Landlord the
full amount of such excess prior to Landlord's delivery of the applicable
portion of the Expansion Space to Tenant. No portion of the Improvement
Allowance shall be used to pay Tenant or Tenant's agents, contractors or
employees, unless and until Landlord's contractors and any other persons and
entities employed by or under contract with Landlord have been paid in full. Any
unused portion of the Over-Allowance Amount will be returned to Tenant promptly
after completion of the Improvements and the receipt of all invoices.

         4.3.2 Landlord Supervision. Landlord shall independently retain
               --------------------
Contractor to construct the Improvements in accordance with the Approved Working
Drawings and the Cost Proposal and Landlord shall supervise the construction by
Contractor, and Tenant shall pay a construction supervision and management fee
(the "Landlord Supervision Fee") to Landlord

                                   EXHIBIT B
                                       -4-
<PAGE>

(or its agent) in an amount equal to the product of (i) five percent (5%) and
(ii) the Construction Costs up to $250,000; plus the product of (a) four percent
(4%) and (b) any Construction Costs from $250,001 to $500,000; plus the product
of (1) three percent (3%) and (2) any Construction Costs above $500,000.

         4.3.3 Contractor's Warranties and Guaranties. Landlord hereby assigns
               --------------------------------------
to Tenant all warranties and guaranties by Contractor relating to the
Improvements, and Tenant hereby waives all claims against Landlord relating to,
or arising out of the construction of, the Improvements (excluding any gross
negligence or willful misconduct of Landlord, which Landlord will be liable for
so long as such amounts are not covered by insurance maintained by Tenant or
required to be maintained by Tenant pursuant to the Lease). Such warranties and
guaranties of Contractor shall guarantee that the Improvements shall be free
from any defects in workmanship and materials for a period of not less than one
(1) year from the date of completion thereof.

     4.4 Phased Construction/Abatement Period. Tenant shall be entitled to elect
         ------------------------------------
either (a) to have Landlord construct the Improvements in Suites 101, 102 and
M-100 after all such Suites are received by Tenant (collectively, the "First
Floor Suites"), or (b) to wait until all portions of the Expansion Space are
received and to have Landlord construct the Improvements (i) in the entire
Expansion Space simultaneously or (ii) in two (2) phases, one (1) phase being
the First Floor Suites and the other phase being Suite 310, in order to permit
Tenant to conduct business in the portion not under construction (for example,
construction may proceed in the First Floor Suites while Tenant conducts
business in Suite 310, and once construction in the First Floor Suites is
complete, construction in Suite 310 would commence and Tenant would conduct
business in the First Floor Suites). Tenant shall provide written notice to
Landlord stating which of the foregoing options Tenant elects, and the proposed
dates for commencement of construction of the Improvements, which notice may be
delivered at any time after Landlord's delivery of the First Floor Suites
through the date which is ten (10) days after Landlord's delivery of the last
portion of the Expansion Space being added pursuant to this Amendment. After
Tenant's delivery of such notice to Landlord, Landlord shall exercise all due
diligence to commence and complete construction as soon as practicable. During
the construction of Improvements in the first Floor Suites and/or Suite 310, as
applicable, Tenant's obligation to pay Base Rent for the portion of the
Expansion Space under construction (i.e., the First Floor Suites and/or Suite
310, as applicable) shall be abated. The abatement period will commence as of
the date physical construction of Improvements (as opposed to space planning and
design) begins in any portion of the First Floor Space and/or Suite 310, as
applicable, and shall end as to the First Floor Space and/or Suite 310, as
applicable, on the date such portion of the Expansion Space is "Substantially
Completed" (subject to the provisions of Section 5.2 below) as defined in
Section 5.1 below ("Abatement Period"). Depending upon the scope of work to be
performed, Landlord may require that Tenant vacate the applicable portion(s) of
the Expansion Space during the Abatement Period in order to facilitate the
construction process; provided that Landlord and Tenant will cooperate to
minimize interference with Tenant's business operations so long as any
compromises or other concessions do not delay the Substantial Completion of the
Improvements.

                                    SECTION 5

                         COMPLETION OF THE IMPROVEMENTS;
                         -------------------------------
                           EXPANSION COMMENCEMENT DATE
                           ---------------------------

     5.1 Ready for Occupancy. For purposes of this Lease, "Substantial
         -------------------
Completion" of the First Floor Suites and/or Suite 310, as applicable, shall
occur upon completion of construction of the Improvements in the First Floor
Suites and/or Suite 310, as applicable, pursuant to the Approved Working
Drawings, with the exception of any punch list items and any Tenant fixtures,
work-stations, built-in furniture, or equipment to be installed by Tenant or
under the supervision of Contractor, together with a sign off by the building
inspector or the issuance of a temporary certificate of occupancy (to the extent
such items are required given the scope of the Improvements constructed in the
First Floor Suites and/or Suite 310, as applicable).

     5.2 Delay of Substantial Completion of the Expansion Space. Except as
         ------------------------------------------------------
provided in this Section 5, the applicable Abatement Period shall expire as set
forth in Section 4.4 above. If there shall be a delay or there are delays in the
Substantial Completion of the First Floor Suites and/or Suite 310, as
applicable, as reasonably determined by the Architect or in the occurrence of
any of the other conditions precedent to the Substantial Completion of the
Improvements therein,

                                    EXHIBIT B
                                       -5-
<PAGE>

as a direct, indirect, partial, or total result of any of the following
(collectively, "Tenant Delays"):

         5.2.1 Tenant's failure to comply with the Time Deadlines;

         5.2.2 Tenant's failure to timely approve any matter requiring Tenant's
approval;

         5.2.3 A breach by Tenant of the terms of this Tenant Work Letter or the
Lease;

         5.2.4 Tenant's request for changes in the Approved Working Drawings;

         5.2.5 Tenant's requirement for materials, components, finishes or
improvements which are not available in a reasonable time which are different
from, or not included in, the Standard Improvement Package;

         5.2.6 Changes to the Base, Shell and Core work required by the Approved
Working Drawings to the extent such changes are due to Tenant's particular use
of the Premises and would not typically be found in general office space, but
excluding delays caused by Necessary Mezzanine Changes; or

         5.2.7 Any other acts or omissions of Tenant, or its agents, or
employees (provided that as to a Tenant Delay pursuant to this section 5.2.7,
Landlord shall provide written notice to Tenant specifying the action or
inaction that Landlord contends constitutes a Tenant Delay pursuant to this
Section 5.2.7, and if such action or inaction is not cured within one (1) day
after receipt of such notice, then a Tenant Delay, as set forth in such notice,
shall be deemed to have occurred commencing as of the date such notice is
received and continuing for the number of days the construction of the
Improvements was in fact delayed as a result of such action or inaction);

then, notwithstanding anything to the contrary set forth in this Amendment and
regardless of the actual date of the Substantial Completion of the First Floor
Suites and/or Suite 310, as applicable, the date of expiration of the Abatement
Period shall be deemed to be the date Substantial Completion of the First Floor
Suites and/or Suite 310, as applicable, would have occurred if no Tenant Delays,
as set forth above, had occurred.

                                    SECTION 6

                                  MISCELLANEOUS
                                  -------------

     6.1 Tenant's Entry Into the Expansion Space Prior to Substantial
         ------------------------------------------------------------
Completion. Provided that Tenant and its agents do not interfere with, or delay,
----------
Contractor's work in the Building and the Expansion Space, Landlord shall allow
Tenant access to the portion of the Expansion Space under construction during
the construction of the Improvements therein and prior to the Substantial
Completion of such portion of the Expansion Space for the purpose of Tenant
installing overstandard equipment or fixtures (including Tenant's data and
telephone equipment) in such portion of the Expansion Space. Prior to Tenant's
entry into such portion of the Expansion Space as permitted by the terms of this
Section 6.1, Tenant shall submit a schedule to Landlord and Contractor, for
their approval, which schedule shall detail the timing and purpose of Tenant's
entry. Tenant shall hold Landlord harmless from and indemnify, protect and
defend Landlord against any loss or damage to the Building or Expansion Space
and against injury to any persons caused by Tenant's actions pursuant to this
Section 6.1.

     6.2 Tenant's Representative. Tenant has designated Peter Seidenberg as its
         -----------------------
sole representative with respect to the matters set forth in this Tenant Work
Letter, who shall have full authority and responsibility to act on behalf of the
Tenant as required in this Tenant Work Letter.

     6.3 Landlord's Representative. Landlord has designated Rick Jones of PM
         -------------------------
Realty Group as its sole representative with respect to the matters set forth in
this Tenant Work Letter, who, until further notice to Tenant, shall have full
authority and responsibility to act on behalf of the Landlord as required in
this Tenant Work Letter.

     6.4 Time of the Essence in This Tenant Work Letter. Unless otherwise
         ----------------------------------------------
indicated, all references herein to a "number of days" shall mean and refer to
calendar days. In all instances where Tenant is required to approve or deliver
an item, if no written notice of approval is given

                                    EXHIBIT B
                                       -6-
<PAGE>

or the item is not delivered within the stated time period, at Landlord's sole
option, at the end of said period the item shall automatically be deemed
approved or delivered by Tenant and the next succeeding time period shall
commence.

     6.5 Tenant's Lease Default. Notwithstanding any provision to the contrary
         ----------------------
contained in the Lease, if an event of default as described in Section 17.1 of
the Lease or this Tenant Work Letter has occurred at any time on or before the
Substantial Completion of the Expansion Space, then (i) in addition to all other
rights and remedies granted to Landlord pursuant to the Lease, Landlord shall
have the right to withhold payment of all or any portion of the Improvement
Allowance and/or Landlord may cause Contractor to cease the construction of the
Expansion Space (in which case, Tenant shall be responsible for any delay in the
Substantial Completion of the Expansion Space caused by such work stoppage as
set forth in Section 5.2 of this Tenant Work Letter), and (ii) all other
obligations of Landlord under the terms of this Tenant Work Letter shall be
forgiven until such time as such default is cured pursuant to the terms of this
Lease.

     6.6 Tenant's Agents. All of Tenant's agents, contractors, and
         ---------------
subcontractors performing work in, or in connection with, the Expansion Space
(collectively as "Tenant's Agents"), shall be subject to Landlord's reasonable
approval and, if deemed necessary by Landlord to maintain harmony among other
labor at the Building or if required by law or any agreement to which Landlord
is bound, shall be union labor.

     6.7 Insurance Requirements. All of Tenant's Agents shall carry liability
         ----------------------
and Products and Completed Operation Coverage insurance, each in amounts not
less than One Million Dollars ($1,000,000.00) per incident, One Million Dollars
($1,000,000.00) in aggregate, and in form and with companies as are required to
be carried by Tenant as set forth in Article 9.3 of the Lease, and the policies
therefor shall insure Landlord and Tenant, as their interests may appear, as
well as Landlord's contractor, and shall name as additional insureds all
mortgagees of the Building or any other party designated by Landlord. All
insurance maintained by Tenant's Agents shall preclude subrogation claims by the
insurer against anyone insured thereunder. Such insurance shall provide that it
is primary insurance as respects the Landlord and that any other insurance
maintained by Landlord is excess and noncontributing with the insurance required
hereunder.

                                    EXHIBIT B
                                       -7-<PAGE>

                                                                    Exhibit 10.9

                            PLUMTREE SOFTWARE, INC.
                          235 Pine Street, 16th Floor
                        San Francisco, California 94104

July 27, 1998

John Kunze
325 University Avenue
Menlo Park, CA 94025

Dear John:

     I am delighted to extend to you this employment offer as President and
Chief Executive Officer of Plumtree Software, Inc. (the "Company") reporting to
the Board of Directors. This letter outlines commitments that we have verbally
communicated.

     Your base salary will be $200,000 per annum, payable in accordance with the
Company's standard practices. For the year ended December 31, 1999, you will be
eligible to receive a bonus in addition to your base salary in an amount of up
to $100,000, or fifty percent of your base salary. Payment of the bonus will be
payable following that year end to the extent that you and the Company realize
objectives to be established by you and the Board of Directors for that fiscal
year (the "CEO Objectives"). Realization of such goals will reasonably and
conclusively be determined by the Board of Directory. No bonus will be payable
for the year ended December 31, 1998. In addition, in the even that your
employment is terminated without cause, as reasonably and conclusively
determined by the Board of Directors, the Company will pay you an additional (i)
twelve months of base salary at the time of termination, if terminated prior to
one year from your employment commencement date, or (ii) six months of base
salary at the time of termination, if terminated any time thereafter. For the
purposes of this letter: (a) "cause" means a willful act or omission involving
material injury to the Company, gross misconduct or fraud; willful disobedience
of reasonable directives of the Board; or conviction of a felony; and (b) your
employment will be deemed to have been terminated by the Company without cause
if you resign following any material reduction in your compensation and
benefits, title or duties (measures against those described herein) or the
Company's requirement that you move your primary business location more than
fifty miles from San Francisco.
<PAGE>

     In addition, you will receive options to purchase 921,363 shares of the
Company's Common Stock (the "First Option") pursuant to the Company's 1997
Equity Incentive Plan (the "Plan"). Twenty-five percent of such options will
vest upon your commencement of employment with the Company; provided, that the
Company shall have a right of repurchase of these shares at the exercise price
in the event that you terminate your employment or the Company terminates your
employment for cause, as reasonably and conclusively determined by the Board of
Directors, during the first year of your employment. The remaining options will
vest in equal amounts commencing after twelve months of continuous employment at
the rate of 1/36th of such remaining options per month. All such options will
vest after four years of employment at the Company. The exercise price of such
options will be equal to the fair market value of the Company's Common Stock, as
determined by the Board of Directors, at a meeting of the Board of Directors
following your acceptance of this offer.

     You also will receive options to purchase 230,341 shares of the Company's
Common Stock pursuant to the Plan (the "Second Option," and, together with the
First Option, the "Options"). These options will commence vesting on January 1,
2000 in the event that you and the Company realize all of the CEO Objectives.
Realization of such objectives will reasonably and conclusively be determined by
the Board of Directors. In such event, upon twelve months of continuous
employment thereafter, (January 1, 2001), 25% of such options will vest. The
remaining options will vest in equal amounts thereafter at the rate of 1/36th of
such remaining options per month. The exercise price of such options will be
equal to the fair market value of the Company's Common Stock, as determined by
the Board of Directors, at a meeting of the Board of Directors following your
acceptance of this offer. If the CEO Objectives are not met by you, the option
will vest in its entirety on the seventh anniversary of the option grant date if
you then are a continuing employee of the Company. The CEO Objectives will be
determined promptly upon your acceptance of this offer and attached to the
Second Option.

     Fifty percent (50%) of the then unvested shares subject to the Options will
be accelerated in the event of a Change of Control of the Company, as
hereinafter defined; provided, that no shares shall vest with respect to the
Second Option in the event that the Change of Control occurs or is agreed to
prior to December 31, 1999; and provided further, that no shares of either
Option shall be accelerated in the event that the Company determines that such
acceleration may prohibit the Company from accounting for the Change of Control
transaction as a "pooling of interests." For purposes of this paragraph, a
Change of Control shall be as set forth in the Com-

                                       2
<PAGE>

pany's Articles of Incorporation, which includes (i) an acquisition of the
Company by means of a merger or other form of corporate reorganization in which
outstanding shares of the Company are exchanged for securities or other
consideration issued, or caused to be issued, by the acquiring corporation or
its subsidiary (other than a mere reincorporation transaction) or (ii) a sale of
all or substantially all of the assets of the Company.

     The Company presently provides medical and dental coverage for its
employees and their eligible dependents at no additional cost. In addition, the
Company presently provides its employees with vision, life, accidental death and
dismemberment and disability salary continuation insurance. Benefit coverage
begins on the date of your employment with the Company.

     As a condition to your employment, you will be required to sign an
Employee Confidentiality Agreement. In accordance with applicable law, you also
will be required to demonstrate employment eligibility, which includes
verification of your identity and of your authorization to work in the United
States. The Company will request this documentation on your first day at work,
and such documentation must be provided no later than three business dates
thereafter.

     Please understand that your employment will be voluntarily entered into
and for no specific period. As a result, you will be free to resign at any time,
for any reason, or for no reason. Similarly, the Company will be free to
terminate your employment or this at-will employment relationship with you at
any time, with or without cause, subject to the last two sentences of the second
paragraph set forth above.

     The terms described in this letter shall be the terms of your employment
and shall supercede any prior discussions, writings or commitments. Any
additions or modifications must be in writing and signed by you and the
appropriate officer of the Company. The Options shall be subject to the terms
and conditions of the Options and the Plan, which terms and conditions shall be
consistent with but supercede and replace the terms of this letter.

     As we have discussed, you will be elected to the Company's Board of
Directors upon commencement of your employment with the Company.

                                       3
<PAGE>

     We are confident that you have the talent, dedication and enthusiasm to
help us realize our plans at Plumtree. While we recognize that there is much
work to be done, we look forward to building this Company with you.

Very truly yours,

/s/ PIERRE LAMOND
--------------------------------
Pierre Lamond
Acting Chief Executive Officer

ACCEPTED AND AGREED:

/s/ JOHN KUNZE
--------------------------------
John Kunze

                                       4

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