Document:

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                                                                   EXHIBIT 10.11

                           SOFTWARE LICENSE AGREEMENT

                       AETHER INTELLIGENT MESSAGING (AIM)

       This Software License Agreement ("Agreement") is made effective as of the
date last executed below ("Effective Date") by and between Aether Technologies
International, L.L.C. (hereinafter, "Aether" or "Aether Technologies"), located
at 11460 Cronridge Drive, Owings Mills, MD 21117, and AirWeb Corporation (d/b/a
OpenSky Corporation) ("Licensee"), located at 471 Emerson Street, Suite 200,
Palo Alto, CA 94301.

       The parties agree as follows:

       1. Licensed Software. The software to be licensed to Licensee (which
excludes all of Licensee's affiliates, subsidiaries, partnerships, associations
or other entities or legal relationships in whatever form (collectively referred
to as "Licensee's Subsidiaries")), is Aether's AIM software and documentation
(the "Licensed Software"), as described on Exhibit A. The portion of the
Licensed Software described on Exhibit B hereto is referred to herein as the
"Client Code." All references herein to Licensed Software shall include the
Client Code.

       2. License Grant. Subject to the terms of this Agreement, Aether grants
to Licensee a personal, perpetual, worldwide, irrevocable, royalty-free,
non-exclusive and, except as provided in Section 7, non-transferable license to
(a) reproduce, display and use the Licensed Software at any of Licensee's data
centers and (b) reproduce, sublicense and distribute, directly or indirectly
through value added resellers, original equipment manufacturers, system
integrators or other intermediaries, the Client Code solely for use by
Licensee's customers on wireless hardware devices. Before copying the Licensed
Software, Licensee shall provide Aether with 90 days' written notice and Aether
will have the opportunity to make copies of the Licensed Software and install
such copies in additional data centers identified by Licensee. Licensee shall
also have the right to make two copies of the Licensed Software as archival or
backup copies for its own internal use. No rights are granted under this
Agreement to modify the Licensed Software. Except as otherwise provided in this
Section 2, Licensee is expressly prohibited from licensing or distributing the
Licensed Software to any third party, which includes Licensee's Subsidiaries,
without the prior written permission of Aether, and any such attempted license
or distribution is a material breach of this Agreement.

       Licensee acknowledges that the Licensed Software contains intellectual
property belonging exclusively to Aether Technologies. Except as provided
herein, Licensee acknowledges and agrees that this Agreement does not grant any
right, title or interest in and to any patents, copyrights, trade secrets,
trademarks or other property rights or rights of ownership in the Licensed
Software in whatever form. All rights not expressly granted by Aether hereunder
are reserved by Aether Technologies.

       3. License Fee. No fees are due and payable by Licensee to Aether or from
Aether to Licensee for the license granted or services provided pursuant to this
Agreement. Aether has agreed to enter into this Agreement as consideration for
the shares of Series A Preferred Stock of Licensee issued and sold to Aether by
Licensee as set forth in that certain Series A Preferred Stock Purchase
Agreement, dated as of August 9, 1999.

       4. Copyright Notice. OpenSky shall reproduce all copyright notices
contained in the Licensed Software on each copy made by Licensee of the Licensed
Software in whatever form.

<PAGE>   2

       5. Term. This Agreement shall be effective as of the Effective Date and
shall remain in effect until terminated pursuant to this Section 5. Either party
may terminate this Agreement by providing written notice to the other party if
the other party is in material breach of this Agreement and has not remedied
such breach within thirty (30) days of notice thereof. The parties agree that
their respective obligations and applicable limitations under Sections 2
(License Grant), 7 (No Assignment; No Reverse Engineering), 8 (Confidentiality),
9 (Representations and Warranties), 10 (Indemnification), and 11 (Limitation of
Liability) shall survive any expiration or termination of this Agreement and
that any other obligations and duties which by their nature extend beyond the
expiration or termination of this Agreement shall survive any expiration or
termination and shall remain in effect for a period of ten (10) years
thereafter.

       6. Support.

              (a) Aether shall, at Aether's sole expense, provide Licensee with
       all Updates as they become commercially available to Aether's licensees.
       In this Agreement, "Updates" means all new versions of the Licensed
       Software, including all error corrections, patches, work-arounds, fixes,
       enhancements, new versions defined by changes to the version number
       (e.g., 2.0 to 3.0).

              (b) Should Licensee need any custom modifications to the Licensed
       Software, Aether agrees to negotiate in good faith an agreement for the
       provision of such modifications on a time and materials basis.

              (c) If at any time during the term of this Agreement, the Licensed
       Software fails to substantially conform to the Documentation, Aether
       shall, at its option, either modify or replace the Licensed Software to
       conform to the Documentation in a prompt manner after receiving notice of
       any substantial nonconformity from Licensee.

       7. No Assignment; No Reverse Engineering. Neither this Agreement nor the
rights or obligations hereunder, either in whole or in part, may be assigned or
otherwise transferred, whether voluntarily or by operation of law, by Licensee
without the prior written consent of Aether, which consent may be withheld in
Aether's sole discretion, and any attempted transfer or assignment is null and
void and shall be deemed a material breach of this Agreement. Notwithstanding
the foregoing, Licensee may assign this Agreement to an acquirer of all of the
stock or substantially all of the assets of Licensee. Licensee shall not reverse
engineer, reverse compile or disassemble the Licensed Software.

       8. Confidentiality. Licensee hereby acknowledges that the Licensed
Software, embodied in whatever form or media, constitutes a valuable trade
secret belonging to Aether, and Licensee agrees to hold such trade secret in
strict confidence, and not to use or disclose such trade secret, except as
permitted hereunder. Licensee further acknowledges that Aether is the owner of
and retains all title to the Licensed Software recorded on the original media
and all subsequent copies regardless of the form or media.

       9. Representations and Warranties.

              (a) Each party represents and warrants to the other that (i) it
       has the legal right and corporate power and authority to execute,
       deliver, and perform this Agreement, provided that the sole and exclusive
       remedy for a breach of this Subsection 9 as it relates to intellectual
       property rights will be the indemnification obligations (including the
       limits thereto) set forth in Section 10; (ii) its execution, delivery,
       and performance of this Agreement has been duly authorized in accordance
       with all appropriate corporate power and authority; (iii) the individual
       signing this Agreement on its behalf has

<PAGE>   3

       been authorized to execute this Agreement in the capacity set forth under
       such individual's name on the signature page hereof; and (iv) the
       execution, delivery, and performance of this Agreement constitutes its
       legal, valid, and binding obligation enforceable against it in accordance
       with its terms, except as enforcement may be limited by applicable
       bankruptcy, insolvency, reorganization, or other similar laws affecting
       the enforcement of creditors' rights generally and that the remedy of
       specific performance may be subject to judicial discretion.

              (b) Aether represents and warrants to Licensee that the Licensed
       Software will perform substantially in accordance with its Documentation.

       10. Indemnification.

              (a) General. Aether, at its own expense, will indemnify and defend
       Licensee, its employees, representatives, agents and affiliates against
       any claim, suit, action or proceeding based on or arising from a claim
       brought by a third party that the use, copying, display, or distribution
       of the Licensed Software by Licensee as permitted in Section 2 infringes
       in any manner Intellectual Property Right of any third party. In this
       Agreement, "Intellectual Property Rights" means all rights in, to, or
       arising out of: (i) any U.S., international or foreign patent or any
       application therefor and any and all reissues, divisions, continuations,
       renewals, extensions and continuations-in-part thereof; ii) inventions
       (whether patentable or not in any country), invention disclosures,
       improvements, trade secrets, proprietary information, know-how,
       technology and technical data; (iii) copyrights, copyright registrations,
       mask works, mask work registrations, and applications therefor in the
       U.S. or any foreign country, and all other rights corresponding thereto
       throughout the world; (iv) moral rights; and (v) any other proprietary
       rights anywhere in the world similar to those described in this
       definition. Aether's obligations set forth in this Section 10 are
       conditioned on (i) Aether's prompt notice of any indemnified claim, and
       (ii) Licensee permits Aether to assume and control the defense of the
       action, with counsel chosen by Aether. Aether will pay any and all costs,
       damages, and attorneys fees awarded against Licensee in connection with
       or arising from any such claim, suit or proceeding.

              (b) Election of Remedy. In the event that Licensee's ability to
       use the Licensed Software is enjoined due to a claim covered by the
       indemnity obligations set forth in Section 10(a) above, Aether will, at
       its option and expense, either: (i) procure for Licensee the right to use
       the Licensed Software; (ii) replace the infringing material so that it is
       non-infringing; (iii) modify the infringing material so that it is
       non-infringing or, (iv) if none of the above options are reasonably
       available after commercially reasonable attempts by Aether, Aether may,
       at its option, terminate this Agreement.

              (c) Sole and Exclusive Remedy. The foregoing states Aether's
       entire liability and Licensee's sole and exclusive remedy with respect to
       the infringement of intellectual property rights of any third party.

               (d) LIMIT ON INDEMNITY LIABILITY. IN NO EVENT SHALL AETHER'S
       AGGREGATE, CUMULATIVE LIABILITY TO LICENSEE ARISING OUT OF OR RELATING TO
       THE INDEMNITY OBLIGATIONS DESCRIBED IN THIS SECTION 10 EXCEED ONE MILLION
       DOLLARS ($1,000,000). THIS LIMITATION ON LIABILITY IS CUMULATIVE WITH ALL
       PAYMENTS BEING AGGREGATED TO DETERMINE SATISFACTION OF THE LIMIT. THE
       EXISTENCE OF ONE OR MORE CLAIMS OR SUITS UNDER THIS SECTION WILL NOT
       ENLARGE THE LIMIT.

<PAGE>   4

               (e) Warranty Disclaimer. SUBJECT TO AETHER'S OBLIGATIONS UNDER
       SECTION 9(b), AETHER TECHNOLOGIES MAKES NO REPRESENTATIONS OR WARRANTIES
       THAT THE LICENSED SOFTWARE IS FREE OF ERRORS. THE LICENSED SOFTWARE IS
       PROVIDED ON AN "AS IS" BASIS AND ALL RISK IS WITH LICENSEE. SUBJECT TO
       AETHER'S OBLIGATIONS UNDER SECTION 9(b), AETHER TECHNOLOGIES MAKES NO
       WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO ANY MATTER WHATSOEVER.
       IN PARTICULAR, ANY AND ALL WARRANTIES OF MERCHANTABILITY, OR FITNESS FOR
       A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED.

       11. Limitation of Liability. NEITHER PARTY SHALL BE LIABLE TO THE OTHER
PARTY OR ANY THIRD PARTY FOR ANY INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES,
LOSS OF PROFITS OR REVENUE, OR INTERRUPTION OF BUSINESS IN ANY WAY ARISING OUT
OF OR RELATED TO THIS AGREEMENT, REGARDLESS OF THE FORM OF ACTION, WHETHER IN
CONTRACT, TORT (INCLUDING NEGLIGENCE), STRICT PRODUCT LIABILITY OR OTHERWISE,
EVEN IF ANY REPRESENTATIVE OF THE PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGES.

       12. Entire Agreement. This Agreement and any attachments hereto represent
the entire agreement and understanding of the parties with respect to the
subject matter hereof and supersede all prior representations, understandings
and agreements, whether oral or written, with respect to such subject matter.
This Agreement may be modified only by a writing executed by both parties
hereto.

       13. Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of the State of Maryland as such laws are applied to
agreements entered into and to be performed entirely within Maryland between
Maryland residents and by the laws of the United States. The parties hereby
submit to the jurisdiction of the State of Maryland, and the United States
District Court of Maryland, and agree that such tribunals shall have
jurisdiction and venue over all controversies in connection herewith. The
parties exclude in its entirety the application to this Agreement of the United
Nations Convention on Contracts for the International Sale of Goods.

       14. Export Regulations. Licensee shall not export, directly or
indirectly, any information acquired under this Agreement or any products
utilizing any such information to any country for which the U.S. Government or
any agency thereof at the time of export requires an export license or other
government approval without first obtaining such license or approval.

       15. Relationship of the Parties. Each of the parties shall at all times
during the term of this Agreement act as, and shall represent itself to be, an
independent contractor, and not an agent or employee of the other.

        16. Waiver. A waiver of any default hereunder or of any of the terms and
conditions of this Agreement shall not be deemed to be a continuing waiver or a
waiver of any other default or of any other term or condition, but shall apply
solely to the instance to which such waiver is directed. The exercise of any
right or remedy provided in this Agreement shall be without prejudice to the
right to exercise any other right or remedy provided by law or equity, except as
expressly limited by this Agreement.

       17. Injunctive Relief. The copying or use of the Licensed Software in a
manner inconsistent with any provision of this Agreement will cause irreparable
injury to Aether for which Aether will not have an adequate remedy at law.
Aether shall be entitled to equitable relief in court, including but not limited
to temporary restraining orders, preliminary injunctions and permanent
injunctions.

       18. Severability. In the event any provision of this Agreement is found
to be invalid, illegal or unenforceable, the validity, legality and
enforceability of the remaining provisions shall not in any way be affected or

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impaired.

       19. Notices. Any notice provided for or permitted under this Agreement
will be treated as having been given when (a) delivered personally, (b) sent by
confirmed telex or telecopy, (c) sent by commercial overnight courier with
written verification of receipt, or (d) mailed postage prepaid by certified or
registered mail, return receipt requested, to the signatory of the party to be
notified, at the address set forth above, or at such other place of which the
other party has been notified in accordance with the provisions of this Section
19 (Notices). Copies of all notices to Aether shall also be sent to the
following address: Aether Technologies, Attention, Chief Financial Officer,
11460 Cronridge Drive, Owings Mills, MD 21117, telecopy (410) 654-6554. Copies
of all notices to Licensee shall also be sent to the following address: Wilson,
Sonsini, Goodrich & Rosati, Attention: Aaron J. Alter, Esq., 650 Page Mill Road,
Palo Alto, CA 94304, facsimile (650) 493-6811. Notices will be treated as having
been received upon the earlier of actual receipt or five (5) days after posting.

<PAGE>   6

        IN WITNESS WHEREOF, the parties have caused this Agreement to be
executed by their duly authorized representatives effective as of the Effective
Date.

Licensee:                                    Aether Technologies International,
AirWeb Corporation                           L.L.C.:
(d/b/a OpenSky Corporation)

By:  /s/ Michael D. Dolbec                   By: /s/ David S. Oros
   --------------------------------              -------------------------------
Printed: Michael D. Dolbec                   Printed: David S. Oros
        ---------------------------                  ---------------------------
Title:  CFO and Secretary                    Title: Manager
      -----------------------------                -----------------------------
Date:   August 9, 1999                       Date: 8/9/99
     ------------------------------               ------------------------------

<PAGE>   7

                                   SCHEDULE A

                             DETAILED SOFTWARE LIST
    The object code for the software described in the attached documentation
                         and the attached documentation

<PAGE>   8

                                   SCHEDULE B

                           DESCRIPTION OF CLIENT CODE
The object code for the Client Software described in the attached documentation
         and the attached documentation relating to the Client Software<PAGE>   1

                                                                   EXHIBIT 10.12

                                   ONE MARKET
                            SAN FRANCISCO, CALIFORNIA

                             OFFICE LEASE AGREEMENT

                                     BETWEEN

          EOP-ONE MARKET, L.L.C., A DELAWARE LIMITED LIABILITY COMPANY
                                  ("LANDLORD")

                                       AND

                   OMNISKY CORPORATION, A DELAWARE CORPORATION
                                   ("TENANT")

<PAGE>   2

                                TABLE OF CONTENTS

<TABLE>
<S>                                                                                        <C>
I.   BASIC LEASE INFORMATION............................................................    1

II.  LEASE GRANT........................................................................    6

III.   POSSESSION.......................................................................    7

IV.    RENT.............................................................................    8

V.   COMPLIANCE WITH LAWS; USE..........................................................   12

VI.    SECURITY DEPOSIT.................................................................   13

VII.   SERVICES TO BE FURNISHED BY LANDLORD.............................................   14

VIII.  LEASEHOLD IMPROVEMENTS...........................................................   15

IX.    REPAIRS AND ALTERATIONS..........................................................   15

X.   USE OF ELECTRICAL SERVICES BY TENANT...............................................   16

XI.    ENTRY BY LANDLORD................................................................   17

XII.   ASSIGNMENT AND SUBLETTING........................................................   17

XIII.  LIENS............................................................................   19

XIV.   INDEMNITY AND WAIVER OF CLAIMS...................................................   19

XV.    INSURANCE........................................................................   20

XVI.   SUBROGATION......................................................................   20

XVII.    CASUALTY DAMAGE................................................................   20

XVIII.   CONDEMNATION...................................................................   21

XIX.   EVENTS OF DEFAULT................................................................   22

XX.    REMEDIES.........................................................................   22

XXI.   LIMITATION OF LIABILITY..........................................................   24

XXII.    NO WAIVER......................................................................   24

XXIII.  QUIET ENJOYMENT.................................................................   24

XXIV. RELOCATION........................................................................   24

XXV.     HOLDING OVER...................................................................   24

XXVI.    SUBORDINATION TO MORTGAGES; ESTOPPEL CERTIFICATE...............................   25

XXVII.   ATTORNEYS' FEES................................................................   25

XXVIII. NOTICE..........................................................................   25

XXIX. EXCEPTED RIGHTS...................................................................   26

XXX. SURRENDER OF PREMISES..............................................................   26

XXXI. MISCELLANEOUS.....................................................................   26

XXXII. ENTIRE AGREEMENT.................................................................   28
</TABLE>

<PAGE>   3

                             OFFICE LEASE AGREEMENT

        THIS OFFICE LEASE AGREEMENT (the "Lease") is made and entered into as of
the 27th day of July, 2000, by and between EOP-ONE MARKET, L.L.C., a DELAWARE
LIMITED LIABILITY COMPANY ("Landlord") and OMNISKY CORPORATION, a DELAWARE
CORPORATION ("Tenant").

I.      BASIC LEASE INFORMATION.

        A.      "Building" means the 43-story office tower, the 28-story office
                tower, the 6-story base out of which such towers rise, the glass
                enclosed galleria and a portion of the ground floor of the
                Southern Pacific Transportation Company General Office Building,
                together with all appurtenant plazas, subgrade areas and garages
                bounded by Market, Spear, Mission and Steuart Streets in the
                City of San Francisco, California, commonly known as One Market.

        B.      "Rentable Square Footage of the Project" is deemed to be
                1,460,081 square feet.

        C.      "Premises" shall mean: (i) approximately 35,982 rentable square
                feet described as Suite No. 600 on the 6th floor of Spear Tower
                in the Building as shown on EXHIBIT A-1 attached hereto ("the
                "Spear Premises"); and (ii) approximately 65,934 rentable square
                feet consisting of approximately (a) 33,180 rentable square feet
                described as Suite No. 400 on the 4th floor of Steuart Tower
                (the "4th Floor Steuart Premises"), and (b) 32,754 rentable
                square feet described as Suite No. 600 on the 6th floor of
                Steuart Tower (the "6th Floor Steuart Premises") (the 4th Floor
                Steuart Premises and the 6th Floor Steuart Premises are
                collectively referred to herein as the "Steuart Premises") in
                the Building as shown on EXHIBIT A-2 attached hereto. Landlord
                and Tenant acknowledge and agree that for the period prior to
                the Final Commencement Date (as hereinafter defined), the
                "Premises" shall be deemed to be the space that Landlord has
                tendered possession of to Tenant in the required condition.
                Landlord and Tenant further acknowledge and agree that from and
                after the date (the "Final Commencement Date") which is the last
                to occur of (i) the Spear Premises Commencement Date (as
                hereinafter defined), (ii) the 6th Floor Steuart Premises
                Commencement Date (as hereinafter defined), and (iii) the 4th
                Floor Steuart Premises Commencement Date (as hereinafter
                defined), the Spear Premises and the Steuart Premises shall
                collectively be deemed to be and referred to herein as the
                "Premises" and the "Rentable Square Footage of the Premises"
                shall be deemed to be 101,916 square feet. If the Premises
                include one or more floors in their entirety, all corridors and
                restroom facilities located on such full floors shall be
                considered part of the Premises. Landlord and Tenant stipulate
                and agree that the Rentable Square Footage of the Project and
                the Rentable Square Footage of the Premises are correct and
                shall not be remeasured.

        D.      "Base Rent":

                          BASE RENT FOR SPEAR PREMISES

<TABLE>
<CAPTION>
                                          ANNUAL RATE            ANNUAL            MONTHLY
                      PERIOD            PER SQUARE FOOT         BASE RENT         BASE RENT
                      ------            ---------------         ---------         ---------
                 <S>                    <C>                   <C>                <C>
                 1/1/01 - 3/31/05           $75.00            $2,698,650.00      $224,887.50

                 4/1/05 - 3/31/07           $80.00            $2,878,560.00      $239,880.00

                 4/1/07 - 3/31/11           $85.00            $3,058,470.00      $254,872.50
</TABLE>

                                       1
<PAGE>   4

                    BASE RENT FOR 6TH FLOOR STEUART PREMISES

<TABLE>
<CAPTION>
                                          ANNUAL RATE            ANNUAL            MONTHLY
                      PERIOD            PER SQUARE FOOT         BASE RENT         BASE RENT
                      ------            ---------------         ---------         ---------
                 <S>                    <C>                   <C>                <C>
                 1/1/01 - 3/31/05           $75.00            $2,456,550.00      $204,712.50

                 4/1/05 - 3/31/07           $80.00            $2,620,320.00      $218,360.00

                 4/1/07 - 3/31/11           $85.00            $2,784,090.00      $232,007.50
</TABLE>

                    BASE RENT FOR 4TH FLOOR STEUART PREMISES

<TABLE>
<CAPTION>
                                          ANNUAL RATE            ANNUAL            MONTHLY
                      PERIOD            PER SQUARE FOOT         BASE RENT         BASE RENT
                 <S>                    <C>                   <C>                <C>
                 4/1/01 - 3/31/05           $75.00            $2,488,500.00      $207,375.00

                 4/1/05 - 3/31/07           $80.00            $2,654,400.00      $221,200.00

                 4/1/07 - 3/31/11           $85.00            $2,820,300.00      $235,025.00
</TABLE>

                Landlord and Tenant acknowledge and agree that the schedules of
                Base Rent described above are based on the assumption that (i)
                the Spear Premises Term (as hereinafter defined) and the 6th
                Floor Steuart Premises Term (as hereinafter defined) will
                commence on January 1, 2001, and (ii) the 4th Floor Steuart
                Premises Term (as hereinafter defined) will commence on April 1,
                2001. If the Spear Premises Term or the 6th Floor Steuart
                Premises Term, as the case may be, do not commence on January 1,
                2001, or if the 4th Floor Steuart Premises Term does not
                commence on April 1, 2001, the beginning dates set forth in the
                above schedules with respect to the payment of any
                installment(s) of Base Rent due for each applicable space shall
                be appropriately adjusted on a per diem basis and set forth in
                the commencement letter (described in Section I.G. below) to be
                prepared by Landlord. In the event the later to occur of the
                Spear Premises Commencement Date, the 6th Floor Steuart Premises
                Commencement Date, and the 4th Floor Steuart Premises
                Commencement Date is other than April 1, 2001, the effective
                date of all increases in the Base Rent rate set forth above
                shall be adjusted to reflect such change so that the initial
                Base Rent period shall end on the last day of the 48th full
                calendar month after the Final Commencement Date, and all other
                periods for the payment of Base Rent as set forth above shall be
                similarly adjusted as appropriate.

                Landlord and Tenant further acknowledge and agree that the above
                schedules of Base Rent described above are based on the
                prevailing market Base Rent rate as of the date of this Lease
                (the "Initial Base Rent Rate"). Landlord and Tenant agree that
                within 30 days prior to the Commencement Date (as hereinafter
                defined), Landlord shall provide Tenant by written notice
                ("Landlord Initial Notice") the Landlord's opinion of
                Commencement Prevailing Market (as hereinafter defined) Base
                Rent rate for the Spear Premises and each Steuart Premises as of
                the Commencement Date and Landlord and Tenant shall enter into a
                commencement letter (described in Section I.G. below) which
                shall set forth the schedules of Base Rent with respect to the
                applicable Premises. Notwithstanding the foregoing to the
                contrary, Landlord and Tenant agree that the Commencement
                Prevailing Market Base Rent rate shall in no event be less than
                the Initial Base Rent Rate as set forth in the schedule above or
                greater than $87.00 per rentable square foot based upon a
                ten-year average. In the event Tenant disagrees with Landlord's
                determination of the Commencement Prevailing Market Base Rent
                rate for the for the Spear Premises and each Steuart Premises in
                question, Tenant shall, within 10 Business Days after receipt of
                the Landlord Initial Notice, provide Landlord with written
                notice of rejection (the "Initial Rejection Notice"). If Tenant
                fails to provide Landlord with an Initial Rejection Notice
                within such 10 Business Day period, the Base Rent rates as set
                forth in the Landlord Initial Notice shall be binding and
                Landlord and Tenant shall execute a commencement letter setting
                forth the Base Rent rates for the Spear Premises, the 6th Floor
                Steuart Premises and the 4th Floor Steuart Premises, as the case
                may be. If Tenant timely provides Landlord with an Initial
                Rejection

                                       2
<PAGE>   5

                Notice, Landlord and Tenant shall work together in good faith to
                agree upon the applicable Commencement Prevailing Market Base
                Rent rate for the Premises during the Term. Upon agreement,
                Landlord and Tenant shall enter into the commencement letter in
                accordance with the terms and conditions hereof. Notwithstanding
                the foregoing, if Landlord and Tenant are unable to agree upon
                the Commencement Prevailing Market Base Rent rate for the Spear
                Premises and each applicable Steuart Premises within 30 days
                after the date on which Tenant provides Landlord with an Initial
                Rejection Notice, Tenant may elect to subject the process to
                binding arbitration. If Tenant fails to require arbitration by
                providing written notice of Tenant's election to arbitrate (the
                "Arbitration Notice") within 5 days of the expiration of the 30
                day period set forth above, Tenant's failure to deliver the
                Arbitration Notice within such 5 day period shall be deemed to
                be an acceptance of the Commencement Prevailing Market Base Rent
                rate designated by Landlord.

                If Tenant provides Landlord with an Arbitration Notice, Landlord
                and Tenant, within 10 days after the date of the Arbitration
                Notice, shall each simultaneously submit to the other, in a
                sealed envelope, its good faith estimate of the Commencement
                Prevailing Market Base Rent rate (collectively referred to as
                the "Estimates"). If the higher of such Estimates is not more
                than 105% of the lower of such Estimates, then Commencement
                Prevailing Market Base Rent rate shall be the average of the 2
                Estimates. If the Commencement Prevailing Market Base Rent rate
                is not resolved by the exchange of Estimates, Landlord and
                Tenant, within 7 days after the exchange of Estimates, shall
                each select an appraiser to determine which of the 2 Estimates
                most closely reflects the Commencement Prevailing Market Base
                Rent rate for the Spear Premises and each Steuart Premises
                during the initial Term. Each appraiser so selected shall be
                certified as an MAI appraiser or as an ASA appraiser and shall
                have had at least 5 years experience within the previous 10
                years as a commercial real estate appraiser working in the
                downtown San Francisco, California area with working knowledge
                of current commercial rental rates and practices. For purposes
                of this Lease, an "MAI" appraiser means an individual who holds
                an MAI designation conferred by, and is an independent member
                of, the American Institute of Real Estate Appraisers (or its
                successor organization, or in the event there is no successor
                organization, the organization and designation most similar),
                and an "ASA" appraiser means an individual who holds the Senior
                Member designation conferred by, and is an independent member
                of, the American Society of Appraisers (or its successor
                organization, or, in the event there is no successor
                organization, the organization and designation most similar).
                Upon selection, Landlord's and Tenant's appraisers shall work
                together in good faith to agree upon which of the 2 Estimates
                most closely reflects the Commencement Prevailing Market Base
                Rent rate for the Spear Premises and each Steuart Premises
                during the initial Term. The Estimate chosen by such appraisers
                shall be binding on both Landlord and Tenant as the Base Rent
                rate for the Spear Premises and each Steuart Premises during the
                initial Term. If either Landlord or Tenant fails to appoint an
                appraiser within the 7 day period referred to above, the
                appraiser appointed by the other party shall be the sole
                appraiser for the purposes hereof. If the 2 appraisers cannot
                agree upon which of the 2 Estimates most closely reflects the
                Commencement Prevailing Market Base Rent rate within 20 days
                after their appointment, then, within 10 days after the
                expiration of such 20 day period, the 2 appraisers shall select
                a third appraiser meeting the aforementioned criteria. Once the
                third appraiser has been selected as provided for above, then,
                as soon thereafter as practicable but in any case within 14
                days, the third appraiser shall make his determination of which
                of the 2 Estimates most closely reflects the Commencement
                Prevailing Market Base Rent rate and such Estimate shall be
                binding on both Landlord and Tenant as the Base Rent rate for
                the Premises during the initial Term. If the third appraiser
                believes that expert advice would materially assist him, he may
                retain one or more qualified persons, to provide such expert
                advice. The parties shall share equally in the costs of the
                third appraiser and of any experts retained by the third
                appraiser. Any fees of any appraiser, counsel or experts engaged
                directly by Landlord or Tenant, however, shall be borne by the
                party retaining such appraiser, counsel or expert. Tenant shall
                pay Base Rent upon the terms and conditions in effect for the
                Spear Premises and each Steuart Premises during the initial Term
                as set forth in Section I.D. above until such time as the

                                       3
<PAGE>   6

                Commencement Prevailing Market Base Rent rate has been
                determined. Upon such determination, the Base Rent for the Spear
                Premises and each Steuart Premises during the initial Term shall
                be retroactively adjusted to the commencement of the initial
                Term for each applicable portion of the Premises. In such event,
                Tenant shall pay Landlord the amount of any underpayment within
                30 days after the determination thereof. For purposes of this
                section, "Commencement Prevailing Market" shall mean annual
                rental rate per rentable square foot for space comparable to the
                Spear Premises and each Steuart Premises in the Building and
                office buildings comparable to the Building in the downtown
                financial district of San Francisco, California under leases
                being entered into at or about the time that Commencement
                Prevailing Market is being determined giving appropriate
                consideration to tenant concessions, brokerage commissions,
                tenant improvement allowances and the method of allocating
                Expenses and Taxes after factoring out the value of alterations
                made by Tenant to the Premises which were in excess of the
                Allowance provided by Landlord. Notwithstanding the foregoing,
                space leased under the following circumstances shall not be
                considered to be comparable for purposes hereof: (i) the lease
                term is for less than 5 years, (ii) the space is encumbered by
                the option rights of another tenant, or (iii) the space has a
                lack of windows and/or awkward or unusual shape or
                configuration. The foregoing is not intended to be an exclusive
                list of space that will not be considered comparable.

                In addition to the Base Rent hereunder payable as provided
                above, Tenant shall also issue to Landlord certain warrants of
                the Tenant in accordance with the terms of the Warrant Agreement
                (the "Warrant Agreement") which shall be delivered by Tenant to
                Landlord simultaneously with the execution and delivery of the
                Lease, in the form attached hereto as EXHIBIT H. The warrants
                issued pursuant to the Warrant Agreement shall be deemed to be
                Rent (as hereinafter defined) for purposes of this Lease.

        E.      "Tenant's Pro Rata Share": 6.9802% (comprised of 2.4644% for the
                Spear Premises; 2.2433% for the 6th Floor Steuart Premises; and
                2.2725% for the 4th Floor Steuart Premises). Landlord and Tenant
                acknowledge and agree that for the period prior to the Final
                Commencement Date, "Tenant's Pro Rata Share" shall be the total
                of the above percentages with respect to the portion of the
                Premises which Landlord has tendered possession of to Tenant.
                Notwithstanding the foregoing, from and after the Final
                Commencement Date, "Tenant's Pro Rata Share" shall be 6.9802%.

        F.      "Base Year" for Taxes: 2001; "Base Year" for Expenses: 2001.

        G.      "Term": A period of approximately 123 months. The Spear Premises
                Term shall commence on the date (the "Spear Premises
                Commencement Date") which is the later to occur of (a) the date
                the ADA Modifications in the Spear Premises are Substantially
                Complete (as hereinafter defined), and (b) the earlier to occur
                of (i) the date the Initial Alterations and the ADA
                Modifications in the Spear Premises are Substantially Complete,
                and (ii) 60 days after the date Landlord tenders possession of
                the Spear Premises in the required condition, and shall end on
                the Termination Date (as hereinafter defined). The 6th Floor
                Steuart Premises Term shall commence on the date (the "6th Floor
                Steuart Premises Commencement Date") which is the later to occur
                of (a) the date the ADA Modifications and the Bridge
                Modifications (as defined in EXHIBIT D below) in the 6th Floor
                Steuart Premises are Substantially Complete, and (b) the earlier
                to occur of (i) the date the Initial Alterations, the ADA
                Modifications and the Bridge Modifications in the 6th Floor
                Steuart Premises are Substantially Complete, and (ii) 60 days
                after the date Landlord tenders possession of the 6th Floor
                Steuart Premises in the required condition, and shall end on the
                Termination Date. The 4th Floor Steuart Premises Term shall
                commence on the date (the "4th Floor Steuart Premises
                Commencement Date") which is the later to occur of (a) the date
                the ADA Modifications in the 4th Floor Steuart Premises are
                Substantially Complete (if required), and (b) the earlier to
                occur of (i) the date the Initial Alterations and the ADA
                Modifications (if required) are Substantially Complete, and (ii)
                60 days after the date Landlord tenders possession of the 4th
                Floor Steuart Premises in the required condition, and shall end
                on the Termination

                                       4
<PAGE>   7

                Date. For purposes hereof, the Initial Alterations shall be
                "Substantially Complete" on the date that the Initial
                Alterations have been performed, other than any details of
                construction, mechanical adjustment, or other similar matter,
                the non-completion of which does not materially interfere with
                Tenant's use of the Premises. For purposes hereof, the ADA
                Modifications shall be "Substantially Complete" on the date that
                the ADA Modifications have been performed, other than any
                details of construction, mechanical adjustment, or other similar
                matter, the non-completion of which does not materially
                interfere with Tenant's use of the Premises. Notwithstanding the
                foregoing to the contrary, if Landlord is delayed in the
                performance of the ADA Modifications as a result of any Tenant
                Delay(s) (as that term is defined in EXHIBIT D below), the ADA
                Modifications shall be deemed to be "Substantially Complete" on
                the date that Landlord could reasonably have been expected to
                Substantially Complete the ADA Modifications absent any Tenant
                Delay. For purposes hereof, the Bridge Modifications shall be
                "Substantially Complete" on the date that the Bridge
                Modifications have been performed, other than any details of
                construction, mechanical adjustment, or other similar matter,
                the non-completion of which does not materially interfere with
                Tenant's use of the Premises. Notwithstanding the foregoing to
                the contrary, if Landlord is delayed in the performance of the
                Bridge Modifications as a result of any Tenant Delay(s), the
                Bridge Modifications shall be deemed to be "Substantially
                Complete" on the date that Landlord could reasonably have been
                expected to Substantially Complete the Bridge Modifications
                absent any Tenant Delay. The Term shall commence on the earlier
                to occur of the Spear Premises Commencement Date or the 6th
                Floor Steuart Premises Commencement Date or the 4th Floor
                Steuart Premises Commencement Date (the "Commencement Date")
                and, unless terminated early in accordance with this Lease, end
                on the date (the "Termination Date") which is the last day of
                the 120th month after the Final Commencement Date. Landlord and
                Tenant anticipate that the Spear Premises Commencement Date and
                the 6th Floor Steuart Premises Commencement Date shall be
                January 1, 2001, and that the 4th Floor Steuart Premises
                Commencement Date shall be April 1, 2001. Landlord shall use its
                reasonable efforts to tender possession of the Spear Premises by
                the anticipated Spear Premises Commencement Date, the 6th Floor
                Steuart Premises by the anticipated 6th Floor Steuart Premises
                Commencement Date, and the 4th Floor Steuart Premises by the
                anticipated 4th Floor Steuart Premises Commencement Date. In the
                event the Spear Premises Commencement Date or the 6th Floor
                Steuart Premises Commencement Date are not January 1, 2001, or
                in the event the 4th Floor Steuart Premises Commencement Date is
                not April 1, 2001, Landlord and Tenant shall enter into a
                commencement letter agreement in the form attached as EXHIBIT C
                setting forth the actual commencement dates of the applicable
                portion of the Premises.

        H.      Tenant allowance(s): $11.00 per rentable square foot of the
                Premises as more fully described on EXHIBIT D of this Lease.

        I.      "Security Deposit": $11,081,267.00. The Security Deposit shall
                be in the form of an irrevocable letter of credit, as more fully
                described in Article VI of this Lease.

        J.      "Guarantor(s)": As of the date of this Lease, there are no
                Guarantors.

        K.      "Broker(s)": CB Richard Ellis, Inc.

        L.      "Permitted Use": General office use.

                                       5
<PAGE>   8

        M.      "Notice Addresses":

                Tenant:

                On and after the Commencement Date, notices shall be sent to
                Tenant at the Premises, Attention: Legal Department. Prior to
                the Commencement Date, notices shall be sent to Tenant at the
                following address:

                1001 Elwell Court
                Palo Alto, California 94303
                Attention:  Legal Department

<TABLE>
                <S>                                     <C>
                LANDLORD:                               WITH A COPY TO:

                EOP-ONE MARKET, L.L.C., A DELAWARE      Equity Office Properties
                LIMITED LIABILITY COMPANY               Two North Riverside Plaza
                c/o Equity Office Properties            Suite 2200
                One Market                              Chicago, Illinois 60606
                Spear Tower                             Attention: Regional Counsel - Pacific
                Suite 725                               Region
                San Francisco, California  94105
                Attention:  Building Manager
</TABLE>

                Rent (defined in Section IV.A) is payable to the order of EQUITY
                OFFICE PROPERTIES at the following address: EOP OPERATING
                LIMITED PARTNERSHIP, DBA ONE MARKET PLAZA, DEPT #8791, LOS
                ANGELES, CALIFORNIA 90084-8791.

        N.      "Business Day(s)" are Monday through Friday of each week,
                exclusive of New Year's Day, President's Day, Memorial Day,
                Independence Day, Labor Day, Thanksgiving Day and Christmas Day
                ("Holidays"). Landlord may designate additional Holidays,
                provided that the additional Holidays are commonly recognized by
                other office buildings in the area where the Building is
                located.

        O.      "Landlord Work" means the work, if any, that Landlord is
                obligated to perform in the Premises pursuant to a separate work
                letter agreement (the "Work Letter"), if any, attached as
                EXHIBIT D. If a Work Letter is not attached to this Lease or if
                an attached Work Letter does not require Landlord to perform any
                work, the occurrence of the Commencement Date shall not be
                conditioned upon the performance of work by Landlord and,
                accordingly, Section III.A. shall not be applicable to the
                determination of the Commencement Date.

        P.      "Law(s)" means all applicable statutes, codes, ordinances,
                orders, rules and regulations of any municipal or governmental
                entity.

        Q.      "Normal Business Hours" for the Building are 7:00 A.M. to 6:00
                P.M. on Business Days.

        R.      "Project" means the 43-story office tower, the 28-story office
                tower, the 6-story base out of which such towers rise, the glass
                enclosed galleria and a portion of the ground floor of the
                Southern Pacific Transportation Company General Office Building,
                together with all appurtenant plazas, subgrade areas and garages
                bounded by Market, Spear, Mission and Steuart Streets in the
                City of San Francisco, California, known collectively as One
                Market, and the land upon which all of the foregoing is located.

II.     LEASE GRANT.

        Landlord leases the Premises to Tenant and Tenant leases the Premises
from Landlord, together with the right in common with others to use any portions
of the Project that are designated by Landlord for the common use of tenants and
others, such as sidewalks, unreserved parking areas, common corridors, elevator
foyers, restrooms, vending areas and lobby areas (the "Common Areas").

                                       6
<PAGE>   9

III.    POSSESSION.

        A.      INTENTIONALLY OMITTED.

        B.      Subject to Landlord's obligations under Section IX.B. and
                EXHIBIT D attached hereto, the Premises are accepted by Tenant
                in "as is" condition and configuration. By taking possession of
                the Premises, Tenant agrees that the Premises are in good order
                and satisfactory condition, and that there are no
                representations or warranties by Landlord regarding the
                condition of the Premises or the Building. Notwithstanding the
                foregoing to the contrary, Landlord shall use its reasonable
                efforts to ensure that the existing (as of the date of this
                Lease) tenant in each portion of the Premises tenders possession
                of the applicable portion of the Premises to Landlord
                substantially in the condition required pursuant to the terms of
                such tenant's lease; provided that Landlord shall have no
                obligation to bring suit or otherwise incur any costs or
                expenses in connection with such obligation. Notwithstanding the
                foregoing to the contrary, within 15 days after the substantial
                completion of the ADA Modifications and the Bridge
                Modifications, Landlord and Tenant shall together conduct an
                inspection of the ADA Modifications and the Bridge Modifications
                and prepare a "punch list" setting forth any portions of the ADA
                Modifications and the Bridge Modifications that are not in
                conformity with the terms of this Lease. Notwithstanding the
                foregoing, at the request of Landlord, such construction punch
                list shall be mutually prepared by Landlord and Tenant prior to
                the date on which Tenant first begins to move its furniture,
                equipment or other personal property into the Premises.
                Landlord, as part of the ADA Modifications and the Bridge
                Modifications, shall use good faith efforts to correct all such
                items within a reasonable time following the completion of the
                punch list. Notwithstanding anything to the contrary contained
                in this Lease, Landlord shall not be obligated to tender
                possession of any portion of the Premises or other space leased
                by Tenant from time to time hereunder that, on the date
                possession is to be delivered, is occupied by a tenant or other
                occupant or that is subject to the rights of any other tenant or
                occupant, and except as expressly set forth herein with respect
                to Landlord's efforts to deliver such possession, Landlord shall
                have no other obligations to Tenant under this Lease with
                respect to such space until the date Landlord: (i) recaptures
                such space from such existing tenant or occupant; and (2)
                regains the legal right to possession thereof. This Lease shall
                not be affected by any such failure to deliver possession and,
                except as expressly set forth herein with respect to Landlord's
                efforts to deliver such possession, Tenant shall have no claim
                for damages against Landlord as a result thereof, all of which
                are hereby waived and released by Tenant. If Landlord is delayed
                delivering possession of any portion of the Premises or any
                other space due to the holdover or unlawful possession of such
                space by any party, Landlord shall use commercially reasonable
                efforts to obtain possession of the space. In the event Landlord
                is unable to tender possession within thirty (30) days after the
                date on which Landlord is required to deliver possession due to
                the holdover or prior possession of such space by the existing
                tenant, Landlord shall take all legal action reasonably
                necessary to recapture possession of the applicable portion of
                the Premises from such existing tenant and/or regain legal right
                to possession thereof. In such event, the commencement date with
                respect to that portion of the Premises subject to such holdover
                or unlawful possession shall be postponed until the date which
                is the later to occur of (a) the date the ADA Modifications (if
                applicable) and the Bridge Modifications (if applicable) in such
                portion of the Premises are Substantially Complete, and (b) the
                earlier to occur of (i) the date the Initial Alterations, the
                ADA Modifications (if applicable) and the Bridge Modifications
                (if applicable) are Substantially Complete with respect to that
                portion of the Premises, and (ii) 60 days after the date
                Landlord delivers possession of such portion of the Premises to
                Tenant free from occupancy by any party, provided that Landlord
                may tender possession to Tenant of the remaining portion of the
                Premises not subject to such holdover or unlawful possession.
                Notwithstanding the foregoing, if there have been no Tenant
                Delays (as defined in EXHIBIT D attached hereto) and Landlord
                has not delivered possession of any portion of the Premises to
                Tenant by September 1, 2001 (the "Outside Possession Date"),
                Tenant, as its sole remedy, may terminate this Lease with
                respect to only that portion of the Premises which Landlord has
                not tendered possession of to Tenant by giving Landlord written
                notice of termination

                                       7
<PAGE>   10

                on or before 5 Business Days after the Outside Possession Date.
                In such event, this Lease shall be deemed null and void and of
                no further force and effect with respect to such applicable
                portion of the Premises and Landlord shall promptly refund any
                prepaid rent previously advanced by Tenant under this Lease with
                respect to such applicable portion of the Premises and, so long
                as Tenant has not previously defaulted under any of its
                obligations under the Work Letter, the parties hereto shall have
                no further responsibilities or obligations to each other with
                respect to such applicable portion of the Premises. Landlord and
                Tenant acknowledge and agree that the Outside Possession Date
                shall be postponed by the number of days Landlord is delayed in
                delivering possession of such portion of the Premises to Tenant
                due to events of Force Majeure. In the event Tenant elects to
                terminate this Lease with respect to that portion of the
                Premises as provided above, Landlord and Tenant shall enter into
                an amendment to this Lease modifying the Premises, Tenant's Pro
                Rata Share, the Base Rent payable, the Final Commencement Date,
                the amount of the Security Deposit, and such other appropriate
                terms as are required to properly reflect such reduction in the
                Premises. Notwithstanding the foregoing, in no event shall the
                number of warrants issued to Landlord pursuant to the Warrant
                Agreement be adjusted.

        C.      If Tenant takes possession of any portion of the Premises before
                the applicable commencement date for such portion of the
                Premises, such possession shall be subject to the terms and
                conditions of this Lease and Tenant shall pay Rent (defined in
                Section IV.A.) with respect to such portion of the Premises to
                Landlord for each day of possession before the applicable
                commencement date. However, except for the cost of services
                requested by Tenant (if any), Tenant shall not be required to
                pay Rent for any days of possession before the applicable
                commencement date during which Tenant, with the approval of
                Landlord, is in possession of the Premises (or any portion
                thereof) for the sole purpose of performing improvements or
                installing furniture, equipment or other personal property.

IV.     RENT.

        A.      Payments. As consideration for this Lease, Tenant shall pay
                Landlord, without any setoff or deduction, the total amount of
                Base Rent and Additional Rent due for the Term. "Additional
                Rent" means all sums (exclusive of Base Rent) that Tenant is
                required to pay Landlord. Additional Rent and Base Rent are
                sometimes collectively referred to as "Rent". Tenant shall pay
                and be liable for all rental, sales and use taxes (but excluding
                income taxes), if any, imposed upon or measured by Rent under
                applicable Law. For purposes of calculating Expenses for the
                Base Year, Expenses for the Base Year shall include any rental,
                sales and use taxes (but excluding income taxes), if any,
                imposed or measured by Rent under applicable Law during the Base
                Year. Base Rent and recurring monthly charges of Additional Rent
                shall be due and payable in advance on the first day of each
                calendar month without notice or demand, provided that the
                installment of Base Rent for the first full calendar month of
                the Term shall be payable upon the execution of this Lease by
                Tenant. All other items of Rent shall be due and payable by
                Tenant on or before 30 days after billing by Landlord. All
                payments of Rent shall be by good and sufficient check or by
                other means (such as automatic debit or electronic transfer)
                acceptable to Landlord. If Tenant fails to pay any item or
                installment of Rent when due, Tenant shall pay Landlord an
                administration fee equal to 5% of the past due Rent, provided
                that Tenant shall be entitled to a grace period of 5 days after
                Tenant's receipt of written notice of such delinquency from
                Landlord for the first 2 late payments of Rent in a given
                calendar year. If the Term commences on a day other than the
                first day of a calendar month or terminates on a day other than
                the last day of a calendar month, the monthly Base Rent and
                Tenant's Pro Rata Share of any Tax Excess (defined in Section
                IV.B.) or Expense Excess (defined in Section IV.B.) for the
                month shall be prorated based on the number of days in such
                calendar month. Landlord's acceptance of less than the correct
                amount of Rent shall be considered a payment on account of the
                earliest Rent due. No endorsement or statement on a check or
                letter accompanying a check or payment shall be considered an
                accord and satisfaction, and either party may accept the check
                or payment without prejudice to that party's right to recover
                the

                                       8
<PAGE>   11

                balance or pursue other available remedies. Tenant's covenant to
                pay Rent is independent of every other covenant in this Lease.

        B.      Expense Excess and Tax Excess. Tenant shall pay Tenant's Pro
                Rata Share of the amount, if any, by which Expenses (defined in
                Section IV.C.) for each calendar year during the Term exceed
                Expenses for the Base Year (the "Expense Excess") and also the
                amount, if any, by which Taxes (defined in Section IV.D.) for
                each calendar year during the Term exceed Taxes for the Base
                Year (the "Tax Excess"). If Expenses and/or Taxes in any
                calendar year decrease below the amount of Expenses and/or Taxes
                for the Base Year, Tenant's Pro Rata Share of Expenses and/or
                Taxes, as the case may be, for that calendar year shall be $0.
                Landlord shall provide Tenant with a good faith estimate of the
                Expense Excess and of the Tax Excess for each calendar year
                during the Term. On or before the first day of each month,
                Tenant shall pay to Landlord a monthly installment equal to
                one-twelfth of Tenant's Pro Rata Share of Landlord's estimate of
                the Expense Excess and one-twelfth of Tenant's Pro Rata Share of
                Landlord's estimate of the Tax Excess. If Landlord determines
                that its good faith estimate of the Expense Excess or of the Tax
                Excess was incorrect by a material amount, Landlord may provide
                Tenant with a revised estimate. After its receipt of the revised
                estimate, Tenant's monthly payments shall be based upon the
                revised estimate. If Landlord does not provide Tenant with an
                estimate of the Expense Excess or of the Tax Excess by January 1
                of a calendar year, Tenant shall continue to pay monthly
                installments based on the previous year's estimate(s) until
                Landlord provides Tenant with the new estimate. Upon delivery of
                the new estimate, an adjustment shall be made for any month for
                which Tenant paid monthly installments based on the previous
                year's estimate(s). Tenant shall pay Landlord the amount of any
                underpayment within 30 days after receipt of the new estimate.
                Any overpayment shall be refunded to Tenant within 30 days or
                credited against the next due future installment(s) of Rent.

                As soon as is practical following the end of each calendar year,
                Landlord shall furnish Tenant with a statement of the actual
                Expenses and Expense Excess and the actual Taxes and Tax Excess
                for the prior calendar year. If the estimated Expense Excess
                and/or estimated Tax Excess for the prior calendar year is more
                than the actual Expense Excess and/or actual Tax Excess, as the
                case may be, for the prior calendar year, Landlord shall apply
                any overpayment by Tenant against Rent due or next becoming due,
                provided if the Term expires before the determination of the
                overpayment, Landlord shall refund any overpayment to Tenant
                after first deducting the amount of Rent due. If the estimated
                Expense Excess and/or estimated Tax Excess for the prior
                calendar year is less than the actual Expense Excess and/or
                actual Tax Excess, as the case may be, for such prior year,
                Tenant shall pay Landlord, within 30 days after its receipt of
                the statement of Expenses and/or Taxes, any underpayment for the
                prior calendar year.

        C.      Expenses Defined. "Expenses" means all costs and expenses
                reasonably incurred in each calendar year in connection with
                operating, maintaining, repairing, and managing the Building and
                the Project, including, but not limited to:

                1.      Labor costs, including, wages, salaries, social security
                        and employment taxes, medical and other types of
                        insurance, uniforms, training, and retirement and
                        pension plans.

                2.      Management fees, the cost of equipping and maintaining a
                        management office, accounting and bookkeeping services,
                        legal fees not attributable to leasing or collection
                        activity, and other administrative costs. Landlord, by
                        itself or through an affiliate, shall have the right to
                        directly perform or provide any services under this
                        Lease (including management services), provided that the
                        cost of any such services shall not exceed the cost that
                        would have been incurred had Landlord entered into an
                        arms-length contract for such services with an
                        unaffiliated entity of comparable skill and experience.

                                       9
<PAGE>   12

                3.      The cost of services, including amounts paid to service
                        providers and the rental and purchase cost of parts,
                        supplies, tools and equipment.

                4.      Premiums and deductibles paid by Landlord for insurance,
                        including workers compensation, fire and extended
                        coverage, earthquake, general liability, rental loss,
                        elevator, boiler and other insurance customarily carried
                        from time to time by owners of comparable office
                        buildings.

                5.      Electrical Costs (defined below) and charges for water,
                        gas, steam and sewer, but excluding those charges for
                        which Landlord is entitled to reimbursement by tenants.
                        "Electrical Costs" means: (a) charges paid by Landlord
                        for electricity; (b) costs incurred in connection with
                        an energy management program for the Project; and (c) if
                        and to the extent permitted by Law, a fee for the
                        services provided by Landlord in connection with the
                        selection of utility companies and the negotiation and
                        administration of contracts for electricity, provided
                        that such fee shall not exceed 50% of any savings
                        obtained by Landlord. Electrical Costs shall be adjusted
                        as follows: (i) amounts for which Landlord is entitled
                        to reimbursement for above standard electrical
                        consumption shall be deducted from Electrical Costs;
                        (ii) the cost of electricity incurred to provide
                        overtime HVAC to specific tenants (as reasonably
                        estimated by Landlord) shall be deducted from Electrical
                        Costs; and (iii) if Tenant is billed directly for the
                        cost of building standard electricity to the Premises as
                        a separate charge in addition to Base Rent, the cost of
                        electricity to individual tenant spaces in the Building
                        shall be deducted from Electrical Costs.

                6.      The amortized cost of capital improvements (as
                        distinguished from replacement parts or components
                        installed in the ordinary course of business) made to
                        the Project which are: (a) performed primarily to reduce
                        operating expense costs or otherwise improve the
                        operating efficiency of the Project; or (b) required to
                        comply with any Laws that are enacted, or first
                        interpreted to apply to the Project, after the date of
                        this Lease. The cost of capital improvements shall be
                        amortized by Landlord over the lesser of the Payback
                        Period (defined below) or 5 years. The amortized cost of
                        capital improvements may, at Landlord's option, include
                        actual or imputed interest at the rate that Landlord
                        would reasonably be required to pay to finance the cost
                        of the capital improvement. "Payback Period" means the
                        reasonably estimated period of time that it takes for
                        the cost savings resulting from a capital improvement to
                        equal the total cost of the capital improvement.

                If Landlord incurs Expenses for the Project together with one or
                more other buildings or properties, whether pursuant to a
                reciprocal easement agreement, common area agreement or
                otherwise, the shared costs and expenses shall be equitably
                prorated and apportioned between the Project and the other
                buildings or properties. Expenses shall not include: the cost of
                capital improvements (except as set forth in Section IV.C.6.
                above); depreciation; interest (except as provided above for the
                amortization of capital improvements); principal or other
                payments of mortgage and other non-operating debts of Landlord;
                ground lease rental; the cost of repairs or other work to the
                extent Landlord is entitled to be reimbursed by insurance or
                condemnation proceeds; costs in connection with leasing space in
                the Building, including brokerage commissions; lease
                concessions, including rental abatements and construction
                allowances, granted to specific tenants; costs incurred in
                connection with the sale, financing or refinancing of the
                Building; fines, interest and penalties incurred due to the late
                payment of Taxes (defined in Section IV.D) or Expenses;
                organizational expenses associated with the creation and
                operation of the entity which constitutes Landlord; or any
                penalties or damages that Landlord pays to Tenant under this
                Lease or to other tenants in the Building under their respective
                leases; payments for rented equipment, the cost of which would
                constitute a capital expenditure if the equipment were
                purchased, in which event, Section IV.C.6 above would govern the
                determination of whether such costs are included in Expenses;
                any cost or expense related to removal, cleaning, abatement or
                remediation of "hazardous materials" in or about the Building,
                Common Area or

                                       10
<PAGE>   13

                Property, including, without limitation, hazardous substances in
                the ground water or soil, except to the extent such removal,
                cleaning, abatement or remediation is related to the general
                repair and maintenance of the Building, Common Area or Property
                in the ordinary course; all items (including repairs) and
                services for which Tenant or other tenants pay directly to third
                parties or for which Tenant or other tenants reimburse (or are
                required to reimburse) Landlord (other than through Expenses);
                reserves not spent by Landlord by the end of the calendar year
                for which Expenses are paid; Landlord's costs of electricity and
                other services sold or provided to tenants in the Building and
                for which Landlord is entitled to be reimbursed by such tenants
                as a separate additional charge or rental over and above the
                base rent or additional rent payable under the lease with such
                tenant; attorney's fees, costs and disbursements and other
                expenses incurred in connection with negotiations or disputes
                with tenants or other occupants of the Building or with
                prospective tenants (other than attorney's fees, costs and
                disbursements and other expenses incurred by Landlord in seeking
                to enforce Building rules and regulations); rental concessions
                granted to specific tenants and expenses incurred in renovating
                or otherwise improving or decorating, painting, or redecorating
                space for specific tenants, other than ordinary repairs and
                maintenance provided to all tenants; costs incurred by Landlord
                for the repair of structural defects; costs arising out of the
                admitted or adjudicated negligence or willful misconduct of
                Landlord or any Landlord Related Parties (as hereinafter
                defined), or any costs, fines or penalties incurred due to
                violations by Landlord of any law, order, rule or regulations of
                any governmental authority which was in effect (and as enforced)
                as of the Lease Commencement Date except where such costs, fines
                or penalties are incurred by Landlord for violations of any such
                law, order, rule or regulation that is ultimately determined to
                be invalid, or inapplicable. If the Building is not at least
                100% occupied during any calendar year or if Landlord is not
                supplying services to at least 100% of the total Rentable Square
                Footage of the Building at any time during a calendar year,
                Expenses shall be determined as if the Building had been 100%
                occupied and Landlord had been supplying services to 100% of the
                Rentable Square Footage of the Building during that calendar
                year. If Tenant pays for its Pro Rata Share of Expenses based on
                increases over a "Base Year", Expenses for the Base Year shall
                also be determined as if the Building had been 100% occupied and
                Landlord had been supplying services to 100% of the Rentable
                Square Footage of the Building. The extrapolation of Expenses
                under this Section shall be performed by appropriately adjusting
                the cost of those components of Expenses that are impacted by
                changes in the occupancy of the Building.

        D.      Taxes Defined. "Taxes" shall mean: (1) all real estate taxes and
                other assessments on the Building and/or Project (plus 10% of
                the land under the existing Southern Pacific Transportation
                Company General Office Building), including, but not limited to,
                assessments for special improvement districts and building
                improvement districts, taxes and assessments levied in
                substitution or supplementation in whole or in part of any such
                taxes and assessments and the Project's share of any real estate
                taxes and assessments under any reciprocal easement agreement,
                common area agreement or similar agreement as to the Project;
                (2) all personal property taxes for property that is owned by
                Landlord and used in connection with the operation, maintenance
                and repair of the Project; and (3) all costs and fees incurred
                in connection with seeking reductions in any tax liabilities
                described in (1) and (2), including, without limitation, any
                costs incurred by Landlord for compliance, review and appeal of
                tax liabilities. Without limitation, Taxes shall not include any
                income, capital levy, franchise, transfer, capital stock, gift,
                estate or inheritance tax. If an assessment is payable in
                installments, Taxes for the year shall include the amount of the
                installment and any interest due and payable during that year.
                For all other real estate taxes, Taxes for that year shall, at
                Landlord's election, include either the amount accrued, assessed
                or otherwise imposed for the year or the amount due and payable
                for that year, provided that Landlord's election shall be
                applied consistently throughout the Term. If a change in Taxes
                is obtained for any year of the Term during which Tenant paid
                Tenant's Pro Rata Share of any Tax Excess, then Taxes for that
                year will be retroactively adjusted and Landlord shall provide
                Tenant with a credit, if any, based on the adjustment. Likewise,
                if a change is obtained for Taxes for the Base Year, Taxes for
                the Base Year shall be restated and the Tax Excess for all
                subsequent years shall be recomputed.

                                       11
<PAGE>   14

                Tenant shall pay Landlord the amount of Tenant's Pro Rata Share
                of any such increase in the Tax Excess within 30 days after
                Tenant's receipt of a statement from Landlord.

        E.      Audit Rights. Tenant may, within 120 days after receiving
                Landlord's statement of Expenses, give Landlord written notice
                ("Review Notice") that Tenant intends to review Landlord's
                records of the Expenses for that calendar year. Within a
                reasonable time after receipt of the Review Notice, Landlord
                shall make all pertinent records available for inspection that
                are reasonably necessary for Tenant to conduct its review. If
                any records are maintained at a location other than the office
                of the Building, Tenant may either inspect the records at such
                other location or pay for the reasonable cost of copying and
                shipping the records. If Tenant retains an agent to review
                Landlord's records, the agent must be with a licensed CPA firm.
                Tenant shall be solely responsible for all costs, expenses and
                fees incurred for the audit. Within 60 days after the records
                are made available to Tenant, Tenant shall have the right to
                give Landlord written notice (an "Objection Notice") stating in
                reasonable detail any objection to Landlord's statement of
                Expenses for that year. If Tenant fails to give Landlord an
                Objection Notice within the 60 day period or fails to provide
                Landlord with a Review Notice within the 120 day period
                described above, Tenant shall be deemed to have approved
                Landlord's statement of Expenses and shall be barred from
                raising any claims regarding the Expenses for that year. If
                Tenant provides Landlord with a timely Objection Notice,
                Landlord and Tenant shall work together in good faith to resolve
                any issues raised in Tenant's Objection Notice. If Landlord and
                Tenant determine that Expenses for the calendar year are less
                than reported, Landlord shall provide Tenant with a credit
                against the next installment of Rent in the amount of the
                overpayment by Tenant. Likewise, if Landlord and Tenant
                determine that Expenses for the calendar year are greater than
                reported, Tenant shall pay Landlord the amount of any
                underpayment within 30 days. The records obtained by Tenant
                shall be treated as confidential. In no event shall Tenant be
                permitted to examine Landlord's records or to dispute any
                statement of Expenses unless Tenant has paid and continues to
                pay all Rent when due.

V.      COMPLIANCE WITH LAWS; USE.

        A.      The Premises may only be used only for the Permitted Use and for
                no other use whatsoever. Tenant shall not use or permit the use
                of the Premises for any purpose which is illegal, dangerous to
                persons or property or which, in Landlord's reasonable opinion,
                unreasonably disturbs any other tenants of the Building or
                interferes with the operation of the Building. Tenant shall
                comply with all Laws, including the Americans with Disabilities
                Act, regarding the operation of Tenant's business and the use,
                condition, configuration and occupancy of the Premises provided
                that Landlord shall be responsible for performing the ADA
                Modifications and the Bridge Modifications as provided in the
                Work Letter attached hereto as EXHIBIT D. Tenant, within 10 days
                after receipt, shall provide Landlord with copies of any notices
                it receives regarding a violation or alleged violation of any
                Laws. Except to the extent properly included in Expenses,
                Landlord shall be responsible for the cost of correcting any
                violations of Title III of the Americans with Disabilities Act
                (ADA) and other Laws with respect to the Common Areas of the
                Building (including but not limited to ADA issues regarding the
                path of travel in the Common Areas). Notwithstanding the
                foregoing, Landlord shall have the right to contest any alleged
                violation in good faith, including, without limitation, the
                right to apply for and obtain a waiver or deferment of
                compliance, the right to assert any and all defenses allowed by
                law and the right to appeal any decisions, judgments or rulings
                to the fullest extent permitted by law. Landlord, after the
                exhaustion of any and all rights to appeal or contest, will make
                all repairs, additions, alterations or improvements necessary to
                comply with the terms of any final order or judgment. Tenant
                shall comply with the rules and regulations of the Building
                attached as EXHIBIT B and such other reasonable rules and
                regulations adopted by Landlord from time to time. Tenant shall
                also cause its agents, contractors, subcontractors, employees,
                customers, and subtenants to comply with all rules and
                regulations. Landlord shall not knowingly discriminate against
                Tenant in Landlord's enforcement of the rules and regulations.

                                       12
<PAGE>   15

        B.      Nothing herein shall require Tenant to perform any alterations,
                additions or improvements which are necessary to comply with
                Laws with respect to the Common Areas, unless such requirement
                to comply relates to the Common Areas on any floor on which the
                Premises are located and arises directly out of the performance
                of work by Tenant in the Premises or Tenant's particular manner
                of use of the Premises for purposes other than general office
                use. In addition, nothing herein shall require Tenant to comply
                with Laws or requirements of public authorities which require
                the installation of new or additional mechanical, electrical,
                plumbing or fire/life safety systems on a Building-wide basis
                without reference to the particular use of Tenant or any
                Alterations (including the Initial Alterations) performed by
                Tenant ("Building-Wide Laws"). Landlord will, at Landlord's
                expense (except to the extent properly included in Expenses),
                perform all acts required to comply with such Building-Wide Laws
                as the same affect the Premises and the Building.

VI.     SECURITY DEPOSIT.

        A.      The Security Deposit shall be in the form of two irrevocable
                letters of credit (collectively, the "Letter of Credit") which
                shall: (a) be in the amount of $11,081,267.00; (b) be issued on
                the form attached hereto as EXHIBIT G; (c) name Landlord as its
                beneficiary; (d) be drawn on an FDIC insured financial
                institution satisfactory to Landlord; and (e) expire no earlier
                than 1 year following the date of execution of this Lease, and
                shall be subsequently renewed and maintained in effect until 60
                days after the Termination Date of this Lease. Tenant shall
                deliver to Landlord the first letter of credit in the amount of
                $7,387,511.33 upon the execution of this Lease by Tenant. Upon
                the earlier to occur of the Spear Premises Commencement Date,
                the 6th Floor Steuart Premises Commencement Date and the 4th
                Floor Steuart Premises Commencement Date, Tenant shall deliver
                the balance of the Security Deposit to Landlord in the form of
                the second letter of credit in the amount of $3,693,755.67. The
                Security Deposit shall be held by Landlord without liability for
                interest (unless required by Law) as security for the
                performance of Tenant's obligations. The Security Deposit is not
                an advance payment of Rent or a measure of Tenant's liability
                for damages. Landlord may, from time to time, without prejudice
                to any other remedy, use all or a portion of the Security
                Deposit to satisfy past due Rent or to cure any uncured default
                by Tenant if past due or uncured after the expiration of
                applicable notice and cure periods (if any). If Landlord uses
                the Security Deposit, Tenant shall on demand restore the
                Security Deposit to its original amount. Landlord shall return
                any unapplied portion of the Security Deposit to Tenant within
                30 days after the later to occur of: (1) the date Tenant
                surrenders possession of the Premises to Landlord in accordance
                with this Lease; or (2) the date this Lease terminates. If
                Landlord transfers its interest in the Premises, Landlord shall
                assign the Security Deposit to the transferee and, following the
                assignment, provided such transferee assumes Landlord's
                liability hereunder in writing, Landlord shall have no further
                liability for the return of the Security Deposit. Landlord shall
                not be required to keep the Security Deposit separate from its
                other accounts.

        B.      Notwithstanding anything herein to the contrary, provided Tenant
                is not in default under this Lease beyond applicable notice and
                cure periods (if any), Tenant shall have the right to reduce the
                amount of the Security Deposit (i.e., the Letter of Credit) by
                $1,108,126.70 in total (i.e. so that the combined reduction in
                both letters of credit together total $1,108,126.70) effective
                as of the second anniversary of the Commencement Date and again
                on each subsequent anniversary of the Commencement Date (each
                such date is hereinafter referred to as a "Reduction Date")
                provided that in each such instance Tenant has successfully
                satisfied all of the Benchmarks (as hereinafter defined) during
                each of the three most recent consecutive fiscal quarters prior
                to the applicable Reduction Date. For purposes hereof, the
                "Benchmarks" shall mean that Tenant shall have satisfied each of
                the following requirements as determined in accordance with
                generally accepted accounting principles based upon audited
                financial statements prepared by an independent certified
                accountant, during each of the three most recent consecutive
                fiscal quarters prior to the applicable Reduction Date: (i)
                Tenant's net worth shall be greater or equal to One Billion
                Dollars; (ii) Tenant's current ratio is at least 2:1; and (iii)
                Tenant's return on equity

                                       13
<PAGE>   16

                is at least 10%. As a condition to Tenant's right to reduce the
                amount of the Security Deposit as provided herein, Tenant shall
                provide such audited financial statements evidencing the
                satisfaction of the Benchmarks to Landlord. In the event Tenant
                fails to satisfy each of the Benchmarks during each of the three
                most recent consecutive fiscal quarters prior to any applicable
                Reduction Date, then Tenant shall have no right to reduce the
                amount of the Letter of Credit on such applicable Reduction
                Date, and any subsequent right of Tenant to reduce the Letter of
                Credit on any subsequent Reduction Date shall not be a
                cumulative right so that the amount of any reduction in the
                Letter of Credit shall never be greater than $1,108,126.70. Such
                reduction shall be accomplished by having Tenant provide
                Landlord with a substitute Letter of Credit in the form of the
                letter of credit attached hereto as EXHIBIT G in the reduced
                amount.

VII.    SERVICES TO BE FURNISHED BY LANDLORD.

        A.      Landlord agrees to furnish Tenant with the following services:
                (1) Water service for use in the lavatories and other
                appropriate facilities approved by Landlord and installed by
                Tenant where water service is needed on each floor on which the
                Premises are located; (2) Heat and air conditioning in season
                during Normal Business Hours, at such temperatures and in such
                amounts as are standard for comparable buildings or as required
                by governmental authority. Tenant, upon such advance notice as
                is reasonably required by Landlord, shall have the right to
                receive HVAC service during hours other than Normal Business
                Hours. Tenant shall pay Landlord the standard charge for the
                additional service as reasonably determined by Landlord from
                time to time. The standard charge for additional after-hours
                ventilation and air conditioning shall be determined by adding
                Landlord's actual out-of-pocket costs to operate such
                after-hours equipment, plus a reasonable charge to cover the
                depreciation and amortization of the equipment used, plus a
                reasonable administrative surcharge. As of the date hereof,
                Landlord's current charge for after-hours ventilation is $20.00
                per hour per zone and $80.00 per hour for each full floor,
                subject to change from time to time. As of the date hereof,
                Landlord's current charge for after-hours air conditioning is
                $65.00 per hour per zone and $260.00 per hour for each full
                floor, subject to change from time to time. In the event Tenant
                requires heat or air conditioning during hours other than Normal
                Business Hours, charges for such services will be prorated by
                Landlord between each requesting user-tenant (if more than one
                tenant in the same service zone requests additional heating or
                air conditioning at the same time) and the proration shall be
                determined by dividing the cost per zone by the number of
                tenants requesting after hours service in a particular zone,
                after adjusting for their respective periods of use; (3)
                Maintenance and repair of the Project as described in Section
                IX.B.; (4) Janitor service on Business Days. If Tenant's use,
                floor covering or other improvements require special services in
                excess of the standard services for the Building, Tenant shall
                pay the additional cost attributable to the special services;
                (5) Elevator service; (6) Electricity to the Premises for
                general office use, in accordance with and subject to the terms
                and conditions in Article X; (7) Access to the Building for
                Tenant and its employees 24 hours a day, 7 days a week, subject
                to the terms of this Lease and such security or monitoring
                systems as Landlord may reasonably impose, including, without
                limitation, sign-in procedures and/or presentation of
                identification cards; and (8) such other services as Landlord
                reasonably determines are necessary or appropriate for the
                Project.

        B.      Landlord's failure to furnish, or any interruption or
                termination of, services due to the application of Laws, the
                failure of any equipment, the performance of repairs,
                improvements or alterations, or the occurrence of any event or
                cause beyond the reasonable control of Landlord (a "Service
                Failure") shall not render Landlord liable to Tenant, constitute
                a constructive eviction of Tenant, give rise to an abatement of
                Rent, nor relieve Tenant from the obligation to fulfill any
                covenant or agreement. However, if the Premises, or a material
                portion of the Premises, is made untenantable for a period in
                excess of 3 consecutive Business Days as a result of the Service
                Failure, then Tenant, as its sole remedy, shall be entitled to
                receive an abatement of Rent payable hereunder during the period
                beginning on the 4th consecutive Business Day of the Service
                Failure and ending on the day the service has been restored. If
                the entire Premises has not been rendered

                                       14
<PAGE>   17

                untenantable by the Service Failure, the amount of abatement
                that Tenant is entitled to receive shall be prorated based upon
                the percentage of the Premises rendered untenantable and not
                used by Tenant. In no event, however, shall Landlord be liable
                to Tenant for any loss or damage, including the theft of
                Tenant's Property (defined in Article XV), arising out of or in
                connection with the failure of any security services, personnel
                or equipment.

VIII.   LEASEHOLD IMPROVEMENTS.

        All improvements to the Premises (collectively, "Leasehold
Improvements") shall be owned by Landlord and shall remain upon the Premises
without compensation to Tenant. However, Landlord, by written notice to Tenant
within 30 days prior to the Termination Date, may require Tenant to remove, at
Tenant's expense: (1) Cable (defined in Section IX.A) installed by or for the
exclusive benefit of Tenant and located in the Premises or other portions of the
Building; and (2) any Leasehold Improvements that are performed by or for the
benefit of Tenant and, in Landlord's reasonable judgment, are of a nature that
would require removal and repair costs that are materially in excess of the
removal and repair costs associated with standard office improvements
(collectively referred to as "Required Removables"). Without limitation, it is
agreed that Required Removables include internal stairways, raised floors,
personal baths and showers, vaults, rolling file systems and structural
alterations and modifications of any type. The Required Removables designated by
Landlord shall be removed by Tenant before the Termination Date, provided that
upon prior written notice to Landlord, Tenant may remain in the Premises for up
to 5 days after the Termination Date for the sole purpose of removing the
Required Removables. Tenant's possession of the Premises shall be subject to all
of the terms and conditions of this Lease, including the obligation to pay Rent
on a per diem basis at the rate in effect for the last month of the Term. Tenant
shall repair damage caused by the installation or removal of Required
Removables. If Tenant fails to remove any Required Removables or perform related
repairs in a timely manner, Landlord, at Tenant's expense, may remove and
dispose of the Required Removables and perform the required repairs. Tenant,
within 30 days after receipt of an invoice, shall reimburse Landlord for the
reasonable costs incurred by Landlord. Notwithstanding the foregoing, Tenant, at
the time it requests approval for a proposed Alteration (defined in Section
IX.C), may request in writing that Landlord advise Tenant whether the Alteration
or any portion of the Alteration will be designated as a Required Removable.
Within 10 days after receipt of Tenant's request, Landlord shall advise Tenant
in writing as to which portions of the Alteration, if any, will be considered to
be Required Removables.

IX.     REPAIRS AND ALTERATIONS.

        A.      Tenant's Repair Obligations. Tenant shall, at its sole cost and
                expense, promptly perform all maintenance and repairs to the
                Premises that are not Landlord's express responsibility under
                this Lease (including, but not limited to such obligations as
                are set forth in Article XVII below), and shall keep the
                Premises in good condition and repair, reasonable wear and tear
                excepted. Tenant's repair obligations include, without
                limitation, repairs to: (1) floor covering; (2) interior
                partitions; (3) doors; (4) the interior side of demising walls;
                (5) electronic, phone and data cabling and related equipment
                (collectively, "Cable") that is installed by or for the
                exclusive benefit of Tenant and located in the Premises or other
                portions of the Building; (6) supplemental air conditioning
                units, private showers and kitchens, including hot water
                heaters, plumbing, and similar facilities installed by or for
                the exclusive benefit of Tenant and serving Tenant exclusively;
                and (7) Alterations performed by contractors retained by Tenant,
                including related HVAC balancing. All work shall be performed in
                accordance with the rules and procedures described in Section
                IX.C. below. If Tenant fails to make any repairs to the Premises
                for more than 30 days after notice from Landlord (although
                notice shall not be required if there is an emergency), Landlord
                may make the repairs, and Tenant shall pay the reasonable cost
                of the repairs to Landlord within 30 days after receipt of an
                invoice, together with an administrative charge in an amount
                equal to 10% of the cost of the repairs.

        B.      Landlord's Repair Obligations. Landlord shall keep and maintain
                in good repair and working order and make repairs to and perform
                maintenance upon: (1) structural elements of the Building; (2)
                mechanical (including HVAC), electrical, plumbing and fire/life
                safety systems serving the Building in general

                                       15
<PAGE>   18

                and the Premises; (3) Common Areas; (4) the roof of the
                Building; (5) exterior windows of the Building; and (6)
                elevators serving the Building. Landlord shall promptly make
                repairs (considering the nature and urgency of the repair) for
                which Landlord is responsible.

        C.      Alterations. Tenant shall not make alterations, additions or
                improvements to the Premises or install any Cable in the
                Premises or other portions of the Building (collectively
                referred to as "Alterations") without first obtaining the
                written consent of Landlord in each instance, which consent
                shall not be unreasonably withheld or delayed. However,
                Landlord's consent shall not be required for any Alteration that
                satisfies all of the following criteria (a "Cosmetic
                Alteration"): (1) is of a cosmetic nature such as painting,
                wallpapering, hanging pictures and installing carpeting; (2) is
                not visible from the exterior of the Premises or Building; (3)
                will not affect the systems or structure of the Building; and
                (4) does not require work to be performed inside the walls or
                above the ceiling of the Premises. However, even though consent
                is not required, the performance of Cosmetic Alterations shall
                be subject to all the other provisions of this Section IX.C.
                Prior to starting work, Tenant shall furnish Landlord with plans
                and specifications reasonably acceptable to Landlord; names of
                contractors reasonably acceptable to Landlord (provided that
                Landlord may designate specific contractors with respect to
                Building systems); copies of contracts; necessary permits and
                approvals; and evidence of contractor's and subcontractor's
                insurance in amounts reasonably required by Landlord. Changes to
                the plans and specifications must also be submitted to Landlord
                for its approval. Alterations shall be constructed in a good and
                workmanlike manner using materials of a quality that is at least
                equal to the quality designated by Landlord as the minimum
                standard for the Building. Landlord may designate reasonable
                rules, regulations and procedures for the performance of work in
                the Building and, to the extent reasonably necessary to avoid
                disruption to the occupants of the Building, shall have the
                right to designate the time when Alterations may be performed.
                Tenant shall reimburse Landlord within 30 days after receipt of
                an invoice for sums paid by Landlord for third party examination
                of Tenant's plans for non-Cosmetic Alterations. In addition,
                within 30 days after receipt of an invoice from Landlord, Tenant
                shall pay Landlord a fee for Landlord's oversight and
                coordination of any non-Cosmetic Alterations (other than the
                Initial Alterations on any of the floors in the Premises, which
                fee is 3% per the Work Letter attached hereto as EXHIBIT D)
                equal to 7% of the cost of the non-Cosmetic Alterations. Upon
                completion, Tenant shall furnish "as-built" plans (except for
                Cosmetic Alterations), completion affidavits, full and final
                waivers of lien in recordable form, and receipted bills covering
                all labor and materials. Tenant shall assure that the
                Alterations comply with all insurance requirements and Laws.
                Landlord's approval of an Alteration shall not be a
                representation by Landlord that the Alteration complies with
                applicable Laws or will be adequate for Tenant's use.

X.      USE OF ELECTRICAL SERVICES BY TENANT.

        A.      Electricity used by Tenant in the Premises shall, at Landlord's
                option, be paid for by Tenant either: (1) through inclusion in
                Expenses (except as provided in Section X.B. for excess usage);
                (2) by a separate charge payable by Tenant to Landlord within 30
                days after billing by Landlord; or (3) by separate charge billed
                by the applicable utility company and payable directly by
                Tenant. Electrical service to the Premises may be furnished by
                one or more companies providing electrical generation,
                transmission and distribution services, and the cost of
                electricity may consist of several different components or
                separate charges for such services, such as generation,
                distribution and stranded cost charges. Landlord shall have the
                exclusive right to select any company providing electrical
                service to the Premises, to aggregate the electrical service for
                the Project and Premises with other buildings, to purchase
                electricity through a broker and/or buyers group and to change
                the providers and manner of purchasing electricity. Landlord
                shall be entitled to receive a fee (if permitted by Law) for the
                selection of utility companies and the negotiation and
                administration of contracts for electricity, provided that the
                amount of such fee shall not exceed 50% of any savings obtained
                by Landlord.

                                       16
<PAGE>   19

        B.      Tenant's use of electrical service shall not exceed, either in
                voltage, rated capacity, use beyond Normal Business Hours or
                overall load, that which Landlord deems to be standard for the
                Building. Standard electrical use for the Building is deemed to
                be 1 kilowatt hour per rentable square foot, per month,
                including lighting. The base building electrical system will
                allow designs of peak electrical loads of up to 4.5 watts per
                square foot (excluding Building Standard lighting requirements).
                If Tenant requests permission to consume excess electrical
                service, Landlord may refuse to consent or may condition consent
                upon conditions that Landlord reasonably elects (including,
                without limitation, the installation of utility service
                upgrades, meters, submeters, air handlers or cooling units), and
                the additional usage (to the extent permitted by Law),
                installation and maintenance costs shall be paid by Tenant.
                Landlord shall have the right to separately meter electrical
                usage for the Premises and to measure electrical usage by survey
                or other commonly accepted methods.

XI.     ENTRY BY LANDLORD.

        Landlord, its agents, contractors and representatives may enter the
Premises to inspect or show the Premises, to clean and make repairs, alterations
or additions to the Premises, and to conduct or facilitate repairs, alterations
or additions to any portion of the Building, including other tenants' premises.
Except in emergencies or to provide janitorial and other Building services after
Normal Business Hours, Landlord shall provide Tenant with reasonable prior
notice of entry into the Premises, which may be given orally. If reasonably
necessary for the protection and safety of Tenant and its employees, Landlord
shall have the right to temporarily close all or a portion of the Premises to
perform repairs, alterations and additions. However, except in emergencies,
Landlord will not close the Premises if the work can reasonably be completed on
weekends and after Normal Business Hours. Entry by Landlord shall not constitute
constructive eviction or entitle Tenant to an abatement or reduction of Rent.
Notwithstanding the foregoing, except in emergency situations as determined by
Landlord, Landlord shall exercise reasonable efforts to perform any entry into
the Premises in a manner that is reasonably designed to minimize interference
with the operation of Tenant's business in the Premises and shall exercise
reasonable efforts to comply with Tenant's reasonable security measures.

XII.    ASSIGNMENT AND SUBLETTING.

        A.      Except in connection with a Permitted Transfer (defined in
                Section XII.E. below), Tenant shall not assign, sublease,
                transfer or encumber any interest in this Lease or allow any
                third party to use any portion of the Premises (collectively or
                individually, a "Transfer") without the prior written consent of
                Landlord, which consent shall not be unreasonably withheld if
                Landlord does not elect to exercise its termination rights under
                Section XII.B below. Without limitation, it is agreed that
                Landlord's consent shall not be considered unreasonably withheld
                if: (1) the proposed transferee's financial condition does not
                meet the criteria Landlord uses to select Building tenants
                having similar leasehold obligations; (2) the proposed
                transferee's business is not suitable for the Building
                considering the business of the other tenants and the Building's
                prestige, or would result in a violation of another tenant's
                rights; (3) the proposed transferee is a governmental agency or
                occupant of the Project; (4) Tenant is in Monetary Default or
                material non-monetary default after the expiration of the notice
                and cure periods in this Lease; or (5) any portion of the
                Building or Premises would likely become subject to additional
                or different Laws as a consequence of the proposed Transfer in a
                manner that has a material adverse impact on Landlord or the
                Building, and, if such impact is limited to the Premises, Tenant
                does not provide adequate assurances to Landlord that the
                adverse impact will be substantially mitigated in a prompt and
                diligent manner at no cost to Landlord. Notwithstanding the
                foregoing, Landlord will not withhold its consent solely because
                the proposed subtenant or assignee is an occupant of the
                Building if Landlord does not have space available for lease in
                the Building that is comparable to the space Tenant desires to
                sublet or assign. For purposes hereof, Landlord shall be deemed
                to have comparable space if it has space available on any floor
                of the Building that is approximately the same size as the space
                Tenant desires to sublet or assign within 6 months of the
                proposed commencement of the proposed sublease or assignment.
                Tenant shall not be entitled to receive monetary damages based
                upon a claim that Landlord unreasonably withheld its consent to
                a proposed

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<PAGE>   20

                Transfer and Tenant's sole remedy shall be an action to enforce
                any such provision through specific performance or declaratory
                judgment. Any attempted Transfer in violation of this Article
                shall, at Landlord's option, be void. Consent by Landlord to one
                or more Transfer(s) shall not operate as a waiver of Landlord's
                rights to approve any subsequent Transfers. In no event shall
                any Transfer or Permitted Transfer release or relieve Tenant
                from any obligation under this Lease.

        B.      As part of its request for Landlord's consent to a Transfer,
                Tenant shall provide Landlord with financial statements for the
                proposed transferee, a complete copy of the proposed assignment,
                sublease and other contractual documents and such other
                information as Landlord may reasonably request. Landlord shall,
                by written notice to Tenant within 25 days of its receipt of the
                required information and documentation, either: (1) consent to
                the Transfer by the execution of a consent agreement in a form
                reasonably designated by Landlord or reasonably refuse to
                consent to the Transfer in writing; or (2) in the event of (i)
                an assignment of this Lease, or (ii) a subletting which would
                (a) result in 50% or more of the Premises in the aggregate being
                sublet and/or (b) result in a sublease of all or a portion of
                the Premises for more than 50% of the then remaining Term,
                except with respect to a Permitted Transfer, exercise its right
                to terminate this Lease with respect to the portion of the
                Premises that Tenant is proposing to assign or sublet. Any such
                termination shall be effective on the proposed effective date of
                the Transfer for which Tenant requested consent. Notwithstanding
                the foregoing, Tenant, within 5 days after receipt of Landlord's
                notice of intent to terminate, may withdraw its request for
                consent to the Transfer. In such event, Landlord's election to
                terminate the Lease in connection with such proposed Transfer
                shall be null and void and of no force and effect. Tenant shall
                pay Landlord a review fee of $750.00 for Landlord's review of
                any Permitted Transfer or requested Transfer, provided if
                Landlord's actual reasonable costs and expenses (including
                reasonable attorney's fees) exceed $750.00, Tenant shall
                reimburse Landlord for its actual reasonable costs and expenses
                in lieu of a fixed review fee.

        C.      Tenant shall pay Landlord 70% of all rent and other
                consideration which Tenant receives as a result of a Transfer
                (other than a Permitted Transfer) that is in excess of the Rent
                payable to Landlord for the portion of the Premises and Term
                covered by the Transfer. Tenant shall pay Landlord for
                Landlord's share of any excess within 30 days after Tenant's
                receipt of such excess consideration. Tenant may (on an
                amortized basis) deduct from the excess all reasonable and
                customary expenses directly incurred by Tenant attributable to
                the Transfer (other than Landlord's review fee), including
                brokerage fees, legal fees and construction costs and related
                fees, e.g. architect, engineering and permitting fees. If Tenant
                is in Monetary Default (defined in Section XIX.A. below),
                Landlord may require that all sublease payments be made directly
                to Landlord, in which case Tenant shall receive a credit against
                Rent in the amount of any payments received (less Landlord's
                share of any excess).

        D.      Except as provided below with respect to a Permitted Transfer,
                if Tenant is a corporation, limited liability company,
                partnership, or similar entity, and if the entity which owns or
                controls a majority of the voting shares/rights at any time
                changes for any reason (including but not limited to a merger,
                consolidation or reorganization other than a merger,
                consolidation or reorganization which would constitute a
                Permitted Transfer as provided below), such change of ownership
                or control shall constitute a Transfer. The foregoing shall not
                apply so long as Tenant is an entity whose outstanding stock is
                listed on a recognized security exchange including NASDAQ, or if
                at least 80% of its voting stock is owned by another entity, the
                voting stock of which is so listed.

        E.      Notwithstanding anything to the contrary contained herein or in
                Section XIII.D., Tenant may assign its entire interest under
                this Lease or sublet the Premises to a wholly owned corporation,
                partnership or other legal entity or affiliate, subsidiary or
                parent of Tenant or to any successor to Tenant by purchase,
                merger, consolidation or reorganization (hereinafter,
                collectively, referred to as "Permitted Transfer") without the
                consent of Landlord, provided: (i) Tenant is not in default
                under this Lease beyond applicable notice and cure periods (if
                any);

                                       18
<PAGE>   21

                (ii) if such proposed transferee is a successor to Tenant by
                purchase, merger, consolidation or reorganization, the
                continuing or surviving entity shall own all or substantially
                all of the assets of Tenant and shall have a net worth which is
                at least equal to the Tenant's net worth at the date of this
                Lease; (iii) such proposed transferee operates the business in
                the Premises for the Permitted Use and no other purpose; and
                (iv) in no event shall any Permitted Transfer release or relieve
                Tenant from any of its obligations under this Lease. Tenant
                shall give Landlord written notice at least 15 days prior to the
                effective date of such Permitted Transfer. As used herein: (a)
                "parent" shall mean a company which owns a majority of Tenant's
                voting equity; (b) "subsidiary" shall mean an entity wholly
                owned by Tenant or at least 50% of whose voting equity is owned
                by Tenant; and (c) "affiliate" shall mean an entity controlled,
                controlling or under common control with Tenant. Notwithstanding
                the foregoing, sale of the shares of equity of any affiliate or
                subsidiary to which this Lease has been assigned or transferred
                other than to another parent, subsidiary or affiliate of the
                original Tenant named hereunder shall be deemed to be an
                assignment requiring the consent of Landlord hereunder.

XIII.   LIENS.

        Tenant shall not permit mechanic's or other liens to be placed upon the
Project, Premises or Tenant's leasehold interest in connection with any work or
service done or purportedly done by or for benefit of Tenant. If a lien is so
placed, Tenant shall, within 10 days of notice from Landlord of the filing of
the lien, fully discharge the lien by settling the claim which resulted in the
lien or by bonding or insuring over the lien in the manner prescribed by the
applicable lien Law. If Tenant fails to discharge the lien, then, in addition to
any other right or remedy of Landlord, Landlord may bond or insure over the lien
or otherwise discharge the lien. Tenant shall reimburse Landlord for any amount
paid by Landlord to bond or insure over the lien or discharge the lien,
including, without limitation, reasonable attorneys' fees (if and to the extent
permitted by Law) within 30 days after receipt of an invoice from Landlord.

XIV.    INDEMNITY AND WAIVER OF CLAIMS.

        A.      Except to the extent caused by the negligence or willful
                misconduct of Landlord or any Landlord Related Parties (defined
                below), Tenant shall indemnify, defend and hold Landlord, its
                trustees, members, principals, beneficiaries, partners,
                officers, directors, employees, Mortgagee(s) (defined in Article
                XXVI) and agents ("Landlord Related Parties") harmless against
                and from all liabilities, obligations, damages, penalties,
                claims, actions, costs, charges and expenses, including, without
                limitation, reasonable attorneys' fees and other professional
                fees (if and to the extent permitted by Law), which may be
                imposed upon, incurred by or asserted against Landlord or any of
                the Landlord Related Parties and arising out of or in connection
                with any damage or injury occurring in the Premises or any acts
                or omissions (including violations of Law) of Tenant, the Tenant
                Related Parties (defined below) or any of Tenant's transferees,
                contractors or licensees.

        B.      Except to the extent caused by the negligence or willful
                misconduct of Tenant or any Tenant Related Parties (defined
                below), Landlord shall indemnify, defend and hold Tenant, its
                trustees, members, principals, beneficiaries, partners,
                officers, directors, employees and agents ("Tenant Related
                Parties") harmless against and from all liabilities,
                obligations, damages, penalties, claims, actions, costs, charges
                and expenses, including, without limitation, reasonable
                attorneys' fees and other professional fees (if and to the
                extent permitted by Law), which may be imposed upon, incurred by
                or asserted against Tenant or any of the Tenant Related Parties
                and arising out of or in connection with the acts or omissions
                (including violations of Law) of Landlord, the Landlord Related
                Parties or any of Landlord's contractors.

        C.      Landlord and the Landlord Related Parties shall not be liable
                for, and Tenant waives, all claims for loss or damage to
                Tenant's business or loss, theft or damage to Tenant's Property
                or the property of any person claiming by, through or under
                Tenant resulting from: (1) wind or weather; (2) the failure of
                any sprinkler, heating or air-conditioning equipment, any
                electric wiring or any gas, water or steam pipes; (3) the
                backing up of any sewer pipe or downspout; (4) the bursting,
                leaking or running of any tank, water closet, drain or other
                pipe;

                                       19
<PAGE>   22

                (5) water, snow or ice upon or coming through the roof,
                skylight, stairs, doorways, windows, walks or any other place
                upon or near the Building; (6) any act or omission of any party
                other than Landlord or Landlord Related Parties; and (7) any
                causes not reasonably within the control of Landlord. Tenant
                shall insure itself against such losses under Article XV below.

XV.     INSURANCE.

        Tenant shall carry and maintain the following insurance ("Tenant's
Insurance"), at its sole cost and expense: (1) Commercial General Liability
Insurance applicable to the Premises and its appurtenances providing, on an
occurrence basis, a minimum combined single limit of $2,000,000.00; (2) All Risk
Project/Business Interruption Insurance, including flood and earthquake, written
at replacement cost value and with a replacement cost endorsement covering all
of Tenant's trade fixtures, equipment, furniture and other personal property
within the Premises ("Tenant's Property"); (3) Workers' Compensation Insurance
as required by the state in which the Premises is located and in amounts as may
be required by applicable statute; and (4) Employers Liability Coverage of at
least $1,000,000.00 per occurrence. Any company writing any of Tenant's
Insurance shall have an A.M. Best rating of not less than A-VIII. All Commercial
General Liability Insurance policies shall name Tenant as a named insured and
Landlord (or any successor), Equity Office Properties Trust, a Maryland real
estate investment trust, EOP Operating Limited Partnership, a Delaware limited
partnership, and their respective members, principals, beneficiaries, partners,
officers, directors, employees, and agents, and other designees of Landlord as
the interest of such designees shall appear, as additional insureds. All
policies of Tenant's Insurance shall contain endorsements that the insurer(s)
shall give Landlord and its designees at least 30 days' advance written notice
of any material change, cancellation, termination or lapse of insurance. Tenant
shall provide Landlord with a certificate of insurance evidencing Tenant's
Insurance prior to the earlier to occur of the Commencement Date or the date
Tenant is provided with possession of the Premises for any reason, and upon
renewals at least 15 days prior to the expiration of the insurance coverage.
Landlord shall maintain so called All Risk property insurance on the Building at
replacement cost value, as reasonably estimated by Landlord. Except as
specifically provided to the contrary, the limits of either party's' insurance
shall not limit such party's liability under this Lease. As of the date of this
Lease, Landlord carries earthquake insurance covering the Building.

XVI.    SUBROGATION.

        Notwithstanding anything in this Lease to the contrary, Landlord and
Tenant hereby waive and shall cause their respective insurance carriers to waive
any and all rights of recovery, claim, action or causes of action against the
other and their respective trustees, principals, beneficiaries, partners,
officers, directors, agents, and employees, for any loss or damage that may
occur to Landlord or Tenant or any party claiming by, through or under Landlord
or Tenant, as the case may be, with respect to Tenant's Property, the Building,
the Premises, any additions or improvements to the Building or Premises, or any
contents thereof, including all rights of recovery, claims, actions or causes of
action arising out of the negligence of Landlord or any Landlord Related Parties
or the negligence of Tenant or any Tenant Related Parties, which loss or damage
is (or would have been, had the insurance required by this Lease been carried)
covered by property insurance.

XVII.   CASUALTY DAMAGE.

        A.      If all or any part of the Premises is damaged by fire or other
                casualty, Tenant shall immediately notify Landlord in writing.
                During any period of time that all or a material portion of the
                Premises is rendered untenantable as a result of a fire or other
                casualty, the Rent shall abate for the portion of the Premises
                that is untenantable and not used by Tenant. Landlord shall have
                the right to terminate this Lease if: (1) the Building shall be
                damaged so that, in Landlord's reasonable judgment, substantial
                alteration or reconstruction of the Building shall be required
                (whether or not the Premises has been damaged); (2) Landlord is
                not permitted by Law to rebuild the Building in substantially
                the same form as existed before the fire or casualty; (3) the
                Premises have been materially damaged and there is less than 1
                year of the Term remaining on the date of the casualty; (4) any
                Mortgagee requires that the insurance proceeds be applied to the
                payment of the mortgage debt; or (5) a material uninsured loss
                to the Building occurs. Landlord may exercise its right to
                terminate this Lease by notifying Tenant in

                                       20
<PAGE>   23

                writing within 90 days after the date of the casualty.
                Notwithstanding the foregoing, Landlord will not be entitled to
                terminate this Lease solely because there is less than 1 year on
                the Term if Tenant has an exercisable right to renew or extend
                the Term and Tenant, within 10 days after the receipt of
                Landlord's notice of termination, validly exercises such right.
                The foregoing shall not prohibit Landlord from exercising its
                right to terminate for any of the other reasons set forth
                herein. If Landlord does not terminate this Lease, Landlord
                shall commence and proceed with reasonable diligence to repair
                and restore the Building and the Leasehold Improvements
                (excluding any Alterations that were performed by Tenant in
                violation of this Lease). However, in no event shall Landlord be
                required to spend more than the insurance proceeds received by
                Landlord. Landlord shall not be liable for any loss or damage to
                Tenant's Property or to the business of Tenant resulting in any
                way from the fire or other casualty or from the repair and
                restoration of the damage. Landlord and Tenant hereby waive the
                provisions of any Law relating to the matters addressed in this
                Article, and agree that their respective rights for damage to or
                destruction of the Premises shall be those specifically provided
                in this Lease. In the event that Landlord has the right to
                terminate this Lease pursuant to this Article XVII, Landlord
                agrees to exercise such right in a nondiscriminatory fashion.
                Consideration of the following factors in arriving at its
                decision shall not be deemed discriminatory: Length of term
                remaining on the lease, time needed to repair and restore, costs
                of repair and restoration not covered by insurance proceeds,
                Landlord's plans to repair and restore common areas serving the
                Premises, Landlord's plans for repair and restoration of the
                Building, and other relevant factors of Landlord's decision as
                long as they are applied to Tenant in the same manner as other
                tenants.

        B.      If all or any portion of the Premises shall be made untenantable
                by fire or other casualty, Landlord shall, with reasonable
                promptness, cause an architect or general contractor selected by
                Landlord to provide Landlord and Tenant with a written estimate
                of the amount of time required to substantially complete the
                repair and restoration of the Premises and make the Premises
                tenantable again, using standard working methods ("Completion
                Estimate"). If the Completion Estimate indicates that the
                Premises cannot be made tenantable within 180 days from the date
                the repair and restoration is started, then regardless of
                anything in Section XVII.A above to the contrary, either party
                shall have the right to terminate this Lease by giving written
                notice to the other of such election within 10 days after
                receipt of the Completion Estimate. Notwithstanding the
                foregoing, if Tenant was entitled to but elected not to exercise
                its right to terminate the Lease and Landlord does not
                substantially complete the repair and restoration of the
                Premises within 2 months after the expiration of the estimated
                period of time set forth in the Completion Estimate, which
                period shall be extended to the extent of any Reconstruction
                Delays, then Tenant may terminate this Lease by written notice
                to Landlord within 15 days after the expiration of such period,
                as the same may be extended. For purposes of this Lease, the
                term "Reconstruction Delays" shall mean: (i) any delays caused
                by the insurance adjustment process; (ii) any delays caused by
                Tenant; and (iii) any delays caused by events of Force Majeure.
                Tenant, however, shall not have the right to terminate this
                Lease if the fire or casualty was caused by the negligence or
                intentional misconduct of Tenant, Tenant Related Parties or any
                of Tenant's transferees, contractors or licensees.

XVIII.  CONDEMNATION.

        Either party may terminate this Lease if the whole or any material part
of the Premises shall be taken or condemned for any public or quasi-public use
under Law, by eminent domain or private purchase in lieu thereof (a "Taking").
Landlord shall also have the right to terminate this Lease if there is a Taking
of any portion of the Building or Project which would leave the remainder of the
Building unsuitable for use as an office building in a manner comparable to the
Building's use prior to the Taking. In order to exercise its right to terminate
the Lease, Landlord or Tenant, as the case may be, must provide written notice
of termination to the other within 45 days after the terminating party first
receives notice of the Taking. Any such termination shall be effective as of the
date the physical taking of the Premises or the portion of the Building or
Project occurs. If this Lease is not terminated, the Rentable Square Footage of
the Project, the Rentable Square Footage of the Premises and Tenant's Pro Rata
Share shall, if

                                       21
<PAGE>   24

applicable, be appropriately adjusted. In addition, Rent for any portion of the
Premises taken or condemned shall be abated during the unexpired Term of this
Lease effective when the physical taking of the portion of the Premises occurs.
All compensation awarded for a Taking, or sale proceeds, shall be the property
of Landlord, any right to receive compensation or proceeds being expressly
waived by Tenant. However, Tenant may file a separate claim at its sole cost and
expense for Tenant's Property, Tenant's lost goodwill and Tenant's reasonable
relocation expenses, provided the filing of the claim does not diminish the
award which would otherwise be receivable by Landlord.

XIX.    EVENTS OF DEFAULT.

        Tenant shall be considered to be in default of this Lease upon the
occurrence of any of the following events of default:

        A.      Tenant's failure to pay when due all or any portion of the Rent,
                if the failure continues for 5 days after written notice to
                Tenant ("Monetary Default").

        B.      Tenant's failure (other than a Monetary Default) to comply with
                any term, provision or covenant of this Lease, if the failure is
                not cured within 30 days after written notice to Tenant.
                However, if Tenant's failure to comply cannot reasonably be
                cured within 30 days, Tenant shall be allowed additional time
                (not to exceed 90 days) as is reasonably necessary to cure the
                failure so long as: (1) Tenant commences to cure the failure
                within 30 days, and (2) Tenant diligently pursues a course of
                action that will cure the failure and bring Tenant back into
                compliance with the Lease. However, if Tenant's failure to
                comply creates a hazardous condition, the failure must be cured
                immediately upon notice to Tenant. In addition, if Landlord
                provides Tenant with notice of Tenant's failure to comply with
                any particular term, provision or covenant of the Lease on 3
                occasions during any 12 month period, Tenant's subsequent
                violation of such term, provision or covenant shall, at
                Landlord's option, be an incurable event of default by Tenant.

        C.      Tenant or any Guarantor becomes insolvent under any applicable
                Federal or State Law, makes a transfer in fraud of creditors or
                makes an assignment for the benefit of creditors, or admits in
                writing its inability to pay its debts when due.

        D.      The leasehold estate is taken by process or operation of Law.

        E       In the case of any ground floor or retail Tenant, Tenant does
                not take possession of, or abandons or vacates all or any
                portion of the Premises.

        F.      Tenant is in default beyond any notice and cure period under any
                other lease or agreement with Landlord, including, without
                limitation, any lease or agreement for parking.

XX.     REMEDIES.

        A.      Upon the occurrence of any event or events of default under this
                Lease after the expiration of applicable notice and cure periods
                (if any), whether enumerated in Article XIX or not, Landlord
                shall have the option to pursue any one or more of the following
                remedies without any notice (except as expressly prescribed
                herein) or demand whatsoever (and without limiting the
                generality of the foregoing, Tenant hereby specifically waives
                notice and demand for payment of Rent or other obligations and
                waives any and all other notices or demand requirements imposed
                by applicable law):

                1.      Terminate this Lease and Tenant's right to possession of
                        the Premises and recover from Tenant an award of damages
                        equal to the sum of the following:

                        (a)     The Worth at the Time of Award of the unpaid
                                Rent which had been earned at the time of
                                termination;

                        (b)     The Worth at the Time of Award of the amount by
                                which the unpaid Rent which would have been
                                earned after termination until

                                       22
<PAGE>   25

                                the time of award exceeds the amount of such
                                Rent loss that Tenant affirmatively proves could
                                have been reasonably avoided;

                        (c)     The Worth at the Time of Award of the amount by
                                which the unpaid Rent for the balance of the
                                Term after the time of award exceeds the amount
                                of such Rent loss that Tenant affirmatively
                                proves could be reasonably avoided;

                        (d)     Any other amount necessary to compensate
                                Landlord for all the detriment either
                                proximately caused by Tenant's failure to
                                perform Tenant's obligations under this Lease or
                                which in the ordinary course of things would be
                                likely to result therefrom; and

                        (e)     All such other amounts in addition to or in lieu
                                of the foregoing as may be permitted from time
                                to time under applicable law.

                        The "Worth at the Time of Award" of the amounts referred
                        to in parts (a) and (b) above, shall be computed by
                        allowing interest at the lesser of a per annum rate
                        equal to: (i) the greatest per annum rate of interest
                        permitted from time to time under applicable law, or
                        (ii) the Prime Rate plus four percent (4%). For purposes
                        hereof, the "Prime Rate" shall be the per annum interest
                        rate publicly announced as its prime or base rate by a
                        federally insured bank selected by Landlord in the State
                        of California. The "Worth at the Time of Award" of the
                        amount referred to in part (c), above, shall be computed
                        by discounting such amount at the discount rate of the
                        Federal Reserve Bank of San Francisco at the time of
                        award plus one percent (1%);

                2.      Employ the remedy described in California Civil Code
                        Section 1951.4 (Landlord may continue this Lease in
                        effect after Tenant's breach and abandonment and recover
                        Rent as it becomes due, if Tenant has the right to
                        sublet or assign, subject only to reasonable
                        limitations); or

                3.      Notwithstanding Landlord's exercise of the remedy
                        described in California Civil Code Section 1951.4 in
                        respect of an event or events of default, at such time
                        thereafter as Landlord may elect in writing, to
                        terminate this Lease and Tenant's right to possession of
                        the Premises and recover an award of damages as provided
                        above in Paragraph XX.A.1.

                B.      The subsequent acceptance of Rent hereunder by Landlord
                        shall not be deemed to be a waiver of any preceding
                        breach by Tenant of any term, covenant or condition of
                        this Lease, other than the failure of Tenant to pay the
                        particular Rent so accepted, regardless of Landlord's
                        knowledge of such preceding breach at the time of
                        acceptance of such Rent. No waiver by Landlord of any
                        breach hereof shall be effective unless such waiver is
                        in writing and signed by Landlord.

                C.      TENANT HEREBY WAIVES ANY AND ALL RIGHTS CONFERRED BY
                        SECTION 3275 OF THE CIVIL CODE OF CALIFORNIA AND BY
                        SECTIONS 1174 (C) AND 1179 OF THE CODE OF CIVIL
                        PROCEDURE OF CALIFORNIA AND ANY AND ALL OTHER LAWS AND
                        RULES OF LAW FROM TIME TO TIME IN EFFECT DURING THE TERM
                        PROVIDING THAT TENANT SHALL HAVE ANY RIGHT TO REDEEM,
                        REINSTATE OR RESTORE THIS LEASE FOLLOWING ITS
                        TERMINATION BY REASON OF TENANT'S BREACH. TENANT ALSO
                        HEREBY WAIVES, TO THE FULLEST EXTENT PERMITTED BY LAW,
                        THE RIGHT TO TRIAL BY JURY IN ANY EVICTION OR FORCIBLE
                        ENTRY AND DETAINER ACTION OR SIMILAR PROCEEDING BASED
                        UPON OR RELATED TO THE SUBJECT MATTER OF THIS LEASE.

                D.      No right or remedy herein conferred upon or reserved to
                        Landlord is intended to be exclusive of any other right
                        or remedy, and each and every right and remedy shall be
                        cumulative and in addition to any other right or remedy
                        given hereunder or now or hereafter existing by
                        agreement, applicable law or in equity. In addition to
                        other remedies provided in this Lease, Landlord shall be
                        entitled, to the extent permitted by applicable law, to
                        injunctive relief, or to a decree

                                       23
<PAGE>   26

                        compelling performance of any of the covenants,
                        agreements, conditions or provisions of this Lease, or
                        to any other remedy allowed to Landlord at law or in
                        equity. Forbearance by Landlord to enforce one or more
                        of the remedies herein provided upon an event of default
                        shall not be deemed or construed to constitute a waiver
                        of such default.

                E.      This Article XX shall be enforceable to the maximum
                        extent such enforcement is not prohibited by applicable
                        law, and the unenforceability of any portion thereof
                        shall not thereby render unenforceable any other
                        portion.

XXI.    LIMITATION OF LIABILITY.

        NOTWITHSTANDING ANYTHING TO THE CONTRARY CONTAINED IN THIS LEASE, THE
LIABILITY OF LANDLORD (AND OF ANY SUCCESSOR LANDLORD) TO TENANT SHALL BE LIMITED
TO THE INTEREST OF LANDLORD IN THE PROJECT. "INTEREST OF LANDLORD IN THE
BUILDING" SHALL INCLUDE ANY ASSETS OF LANDLORD IN THE OPERATION OF THE PROJECT
(PRIOR TO THE DISTRIBUTION OF THE SAME TO ANY PARTNER OR SHAREHOLDER OF LANDLORD
OR ANY OTHER THIRD PARTY) SUCH AS ACCOUNTS RECEIVABLE, RENTS DUE FROM TENANTS,
INSURANCE PROCEEDS, FIXTURES, EQUIPMENT, SUPPLIES, CLAIMS OF ANY NATURE, SORT OR
DESCRIPTION AND ANY OTHER ITEMS DEEMED TO BE ASSETS IN CONNECTION WITH THE
OWNERSHIP, MAINTENANCE AND OPERATION OF THE BUILDING. TENANT SHALL LOOK SOLELY
TO LANDLORD'S INTEREST IN THE PROJECT FOR THE RECOVERY OF ANY JUDGMENT OR AWARD
AGAINST LANDLORD. NEITHER LANDLORD NOR ANY LANDLORD RELATED PARTY SHALL BE
PERSONALLY LIABLE FOR ANY JUDGMENT OR DEFICIENCY. BEFORE FILING SUIT FOR AN
ALLEGED DEFAULT BY LANDLORD, TENANT SHALL GIVE LANDLORD AND THE MORTGAGEE(S)
(DEFINED IN ARTICLE XXVI BELOW) WHOM TENANT HAS BEEN NOTIFIED HOLD MORTGAGES
(DEFINED IN ARTICLE XXVI BELOW) ON THE PROJECT, BUILDING OR PREMISES, NOTICE AND
REASONABLE TIME TO CURE THE ALLEGED DEFAULT.

XXII.   NO WAIVER.

        Either party's failure to declare a default immediately upon its
occurrence, or delay in taking action for a default shall not constitute a
waiver of the default, nor shall it constitute an estoppel. Either party's
failure to enforce its rights for a default shall not constitute a waiver of its
rights regarding any subsequent default. Receipt by Landlord of Tenant's keys to
the Premises shall not constitute an acceptance or surrender of the Premises.

XXIII.  QUIET ENJOYMENT.

        Tenant shall, and may peacefully have, hold and enjoy the Premises,
subject to the terms of this Lease, provided Tenant pays the Rent and fully
performs all of its covenants and agreements within applicable notice and cure
periods. This covenant and all other covenants of Landlord shall be binding upon
Landlord and its successors only during its or their respective periods of
ownership of the Building, and shall not be a personal covenant of Landlord or
the Landlord Related Parties.

XXIV. RELOCATION.

        INTENTIONALLY OMITTED.

XXV.    HOLDING OVER.

        Except for any permitted occupancy by Tenant under Article VIII, if
Tenant fails to surrender the Premises at the expiration or earlier termination
of this Lease, occupancy of the Premises after the termination or expiration
shall be that of a tenancy at sufferance. Tenant's occupancy of the Premises
during the holdover shall be subject to all the terms and provisions of this
Lease and Tenant shall pay an amount equal to 150% of the greater of: (1) the
sum of the Base Rent and Additional Rent due for the period immediately
preceding the holdover; or (2) the fair market gross rental for the Premises as
reasonably determined by Landlord. No holdover by Tenant or payment by Tenant
after the expiration or early termination of this Lease shall be construed to
extend the Term or prevent Landlord from immediate recovery of possession of the
Premises by summary proceedings or otherwise. In addition to the payment of the
amounts provided above, if Landlord is unable to deliver possession of the
Premises to a

                                       24
<PAGE>   27

new tenant, or to perform improvements for a new tenant, as a result of Tenant's
holdover and Tenant fails to vacate the Premises within 15 days after Landlord
notifies Tenant of Landlord's inability to deliver possession, or perform
improvements, Tenant shall be liable to Landlord for all damages, including,
without limitation, consequential damages, that Landlord suffers from the
holdover.

XXVI.   SUBORDINATION TO MORTGAGES; ESTOPPEL CERTIFICATE.

        Tenant accepts this Lease subject and subordinate to any mortgage(s),
deed(s) of trust, ground lease(s) or other lien(s) now or subsequently arising
upon the Premises, the Building or the Project, and to renewals, modifications,
refinancings and extensions thereof (collectively referred to as a "Mortgage").
The party having the benefit of a Mortgage shall be referred to as a
"Mortgagee". This clause shall be self-operative, but upon request from a
Mortgagee, Tenant shall execute a commercially reasonable subordination
agreement in favor of the Mortgagee. In lieu of having the Mortgage be superior
to this Lease, a Mortgagee shall have the right at any time to subordinate its
Mortgage to this Lease. If requested by a successor-in-interest to all or a part
of Landlord's interest in the Lease, Tenant shall, without charge, attorn to the
successor-in-interest. Landlord and Tenant shall each, within 10 days after
receipt of a written request from the other, execute and deliver an estoppel
certificate to those parties as are reasonably requested by the other (including
a Mortgagee or prospective purchaser). The estoppel certificate shall include a
statement certifying that this Lease is unmodified (except as identified in the
estoppel certificate) and in full force and effect, describing the dates to
which Rent and other charges have been paid, representing that, to such party's
actual knowledge, there is no default (or stating the nature of the alleged
default) and indicating other matters with respect to the Lease that may
reasonably be requested. Notwithstanding the foregoing, as a condition precedent
to the subordination of this Lease, Landlord shall be required to provide Tenant
with a non-disturbance, subordination and attornment agreement in favor of
Tenant from any Mortgagee who comes into existence after the Commencement Date.
Such non-disturbance, subordination and attornment agreement in favor of Tenant
shall provide that, so long as Tenant is paying the rent due under the Lease and
is not otherwise in default under the Lease beyond applicable notice and cure
periods, its right to possession and other terms of the Lease shall remain in
full force and effect. Such non-disturbance, subordination and attornment
agreement may include additional time on behalf of the Mortgagee to cure
defaults of the Landlord and provide that (a) neither Mortgagee nor any
successor-in-interest shall be bound by (i) any payment of the Base Rent,
Additional Rent, or other sum due hereunder for more than 1 month in advance or
(ii) any amendment or modification to the Lease made without the express written
consent of Mortgagee or any successor-in-interest; (b) neither Mortgagee nor any
successor-in-interest will be liable for (i) any act or omission or warranties
of any prior landlord (including Landlord), (ii) the breach of any warranties or
obligations relating to construction of improvements on the property or any
tenant finish work performed or to have been performed by any prior landlord
(including Landlord), or (iii) the return of any security deposit, except to the
extent such deposits have been received by Mortgagee; and (c) neither Mortgagee
nor any successor-in-interest shall be subject to any offsets or defenses which
Tenant might have against any prior landlord (including Landlord). Prior to the
Commencement Date, Landlord will use reasonable efforts to obtain a
non-disturbance, subordination and attornment agreement from Landlord's then
current Mortgagee (as of the date of this Lease) in the form of the agreement of
Subordination, Non-Disturber and Attornment attached hereto as EXHIBIT I.
"Reasonable efforts" of Landlord shall not require Landlord to incur any cost,
expense or liability to obtain such agreement, it being agreed that Tenant shall
be responsible for any fee or review costs charged by the Mortgagee. Upon
request of Landlord, Tenant will execute the Mortgagee's commercially reasonable
form of non-disturbance, subordination and attornment agreement and return the
same to Landlord for execution by the Mortgagee. Tenant agrees that the form of
Subordination, Non-Disturber and Attornment Agreement attached hereto as EXHIBIT
I is a commercially reasonable form of non-disturbance, subordination and
attornment agreement. Landlord's failure to obtain a non-disturbance,
subordination and attornment agreement for Tenant prior to the Commencement Date
shall have no effect on the rights, obligations and liabilities of Landlord and
Tenant or be considered to be a default by Landlord hereunder.

XXVII.  ATTORNEYS' FEES.

        If either party institutes a suit against the other for violation of or
to enforce any covenant or condition of this Lease, or if either party
intervenes in any suit in which the other is a party to enforce or protect its
interest or rights, the prevailing party shall be entitled to all of its costs
and expenses, including, without limitation, reasonable attorneys' fees.

                                       25
<PAGE>   28

XXVIII. NOTICE.

        If a demand, request, approval, consent or notice (collectively referred
to as a "notice") shall or may be given to either party by the other, the notice
shall be in writing and delivered by hand or sent by registered or certified
mail with return receipt requested, or sent by overnight or same day courier
service at the party's respective Notice Address(es) set forth in Article I,
except that if Tenant has vacated the Premises (or if the Notice Address for
Tenant is other than the Premises, and Tenant has vacated such address) without
providing Landlord a new Notice Address, Landlord may serve notice in any manner
described in this Article or in any other manner permitted by Law. Each notice
shall be deemed to have been received or given on the earlier to occur of actual
delivery or the date on which delivery is refused, or, if Tenant has vacated the
Premises or the other Notice Address of Tenant without providing a new Notice
Address, 3 Business Days after notice is deposited in the U.S. mail or with a
courier service in the manner described above. Either party may, at any time,
change its Notice Address by giving the other party written notice of the new
address in the manner described in this Article.

XXIX. EXCEPTED RIGHTS.

        This Lease does not grant any rights to light or air over or about the
Building. Landlord excepts and reserves exclusively to itself the use of: (1)
roofs, (2) telephone, electrical and janitorial closets, (3) equipment rooms,
Building risers or similar areas that are used by Landlord for the provision of
Building services, (4) rights to the land and improvements below the floor of
the Premises, (5) the improvements and air rights above the Premises, (6) the
improvements and air rights outside the demising walls of the Premises, and (7)
the areas within the Premises used for the installation of utility lines and
other installations serving occupants of the Building. Landlord has the right to
change the Building's name or address; provided Landlord provides Tenant with
reasonable notice thereof and reimburses Tenant for its actual costs of
replacing all business stationery on hand (not to exceed 2 month's supply).
Landlord also has the right to make such other changes to the Project and
Building as Landlord deems appropriate, provided the changes do not materially
affect Tenant's ability to use the Premises for the Permitted Use. Landlord
shall also have the right (but not the obligation) to temporarily close the
Building if Landlord reasonably determines that there is an imminent danger of
significant damage to the Building or of personal injury to Landlord's employees
or the occupants of the Building. The circumstances under which Landlord may
temporarily close the Building shall include, without limitation, electrical
interruptions, hurricanes and civil disturbances. A closure of the Building
under such circumstances shall not constitute a constructive eviction nor
entitle Tenant to an abatement or reduction of Rent.

XXX. SURRENDER OF PREMISES.

        At the expiration or earlier termination of this Lease or Tenant's right
of possession, Tenant shall remove Tenant's Property (defined in Article XV)
from the Premises, and quit and surrender the Premises to Landlord, broom clean,
and in good order, condition and repair, ordinary wear and tear and damage by
fire or other casualty which Tenant is not required to make, condemnation
repairs which are Landlord's responsibility, and the Initial Alterations (other
than Required Removables) excepted. Tenant shall also be required to remove the
Required Removables in accordance with Article VIII. If Tenant fails to remove
any of Tenant's Property within 2 days after the termination of this Lease or of
Tenant's right to possession, Landlord shall have the right to pursue any
remedies available under Law, including, but not limited to, the remedies
specified in California Civil Code Section 1980 et. seq. with respect to such
Tenant's Property.

XXXI. MISCELLANEOUS.

        A.      This Lease and the rights and obligations of the parties shall
                be interpreted, construed and enforced in accordance with the
                Laws of the State of California and Landlord and Tenant hereby
                irrevocably consent to the jurisdiction and proper venue of such
                state. If any term or provision of this Lease shall to any
                extent be invalid or unenforceable, the remainder of this Lease
                shall not be affected, and each provision of this Lease shall be
                valid and enforced to the fullest extent permitted by Law. The
                headings and titles to the Articles and Sections of this Lease
                are for convenience only and shall have no effect on the
                interpretation of any part of the Lease.

                                       26
<PAGE>   29

        B.      Tenant shall not record this Lease or any memorandum without
                Landlord's prior written consent.

        C.      Landlord and Tenant hereby waive any right to trial by jury in
                any eviction or forcible entry and detainer action or similar
                proceeding based upon, or related to, the subject matter of this
                Lease.

        D.      Whenever a period of time is prescribed for the taking of an
                action by Landlord or Tenant, the period of time for the
                performance of such action shall be extended by the number of
                days that the performance is actually delayed due to strikes,
                acts of God, shortages of labor or materials, war, civil
                disturbances and other causes beyond the reasonable control of
                the performing party ("Force Majeure"). However, events of Force
                Majeure shall not extend any period of time for the payment of
                Rent or other sums payable by either party or any period of time
                for the written exercise of an option or right by either party.

        E.      Landlord shall have the right to transfer and assign, in whole
                or in part, all of its rights and obligations under this Lease
                and in the Building and/or Project referred to herein, and upon
                such transfer Landlord shall be released from any further
                obligations hereunder, and Tenant agrees to look solely to the
                successor in interest of Landlord for the performance of such
                obligations. Notwithstanding the foregoing, unless such
                liability is assumed in writing by its successor in interest
                hereunder, Landlord shall remain liable after its period of
                ownership with respect to any sums due in connection with a
                breach or default that arose during such period of ownership.

        F.      Tenant represents that it has dealt directly with and only with
                the Broker as a broker in connection with this Lease. Tenant
                shall indemnify and hold Landlord and the Landlord Related
                Parties harmless from all claims of any other brokers claiming
                to have represented Tenant in connection with this Lease.
                Landlord agrees to indemnify and hold Tenant and the Tenant
                Related Parties harmless from all claims of any brokers claiming
                to have represented Landlord in connection with this Lease.
                Landlord agrees to pay a brokerage commission to Broker in
                accordance with the terms of a separate written commission
                agreement to be entered into by and between Landlord and Broker,
                provided that in no event shall Landlord be obligated to pay a
                commission to Broker in connection with any extension of the
                Lease Term or in connection with any additional space that is
                leased by Tenant pursuant to the terms of this Lease.

        G.      Tenant covenants, warrants and represents that: (1) each
                individual executing, attesting and/or delivering this Lease on
                behalf of Tenant is authorized to do so on behalf of Tenant; (2)
                this Lease is binding upon Tenant; and (3) Tenant is duly
                organized and legally existing in the state of its organization
                and is qualified to do business in the State of California. If
                there is more than one Tenant, or if Tenant is comprised of more
                than one party or entity, the obligations imposed upon Tenant
                shall be joint and several obligations of all the parties and
                entities. Notices, payments and agreements given or made by,
                with or to any one person or entity shall be deemed to have been
                given or made by, with and to all of them.

        H.      Time is of the essence with respect to Tenant's exercise of any
                expansion, renewal or extension rights granted to Tenant. This
                Lease shall create only the relationship of landlord and tenant
                between the parties, and not a partnership, joint venture or any
                other relationship. This Lease and the covenants and conditions
                in this Lease shall inure only to the benefit of and be binding
                only upon Landlord and Tenant and their permitted successors and
                assigns.

        I.      The expiration of the Term, whether by lapse of time or
                otherwise, shall not relieve either party of any obligations
                which accrued prior to or which may continue to accrue after the
                expiration or early termination of this Lease. Without limiting
                the scope of the prior sentence, it is agreed that Tenant's
                obligations under Sections IV.A, IV.B., VIII, XIV, XX, XXV and
                XXX shall survive the expiration or early termination of this
                Lease.

        J.      Landlord has delivered a copy of this Lease to Tenant for
                Tenant's review only, and the delivery of it does not constitute
                an offer to Tenant or an option. This

                                       27
<PAGE>   30

                Lease shall not be effective against any party hereto until an
                original copy of this Lease has been signed by such party, and
                this Lease has been approved by Landlord's Mortgagee, if
                required. Landlord shall use commercially reasonable efforts to
                obtain the consent of any such Mortgagee. Notwithstanding
                anything to the contrary in this Lease, in the event such
                approval is not obtained within 20 Business Days after execution
                of this Lease by both Landlord and Tenant, either Landlord or
                Tenant shall have the right to terminate this Lease by
                delivering written notice thereof to the other party hereto
                within 10 days after the expiration of such 30 day period.

        K.      All understandings and agreements previously made between the
                parties are superseded by this Lease, and neither party is
                relying upon any warranty, statement or representation not
                contained in this Lease. This Lease may be modified only by a
                written agreement signed by Landlord and Tenant.

        L.      Tenant, within 15 days after request, shall provide Landlord
                with a current financial statement and such other information as
                Landlord may reasonably request in order to create a "business
                profile" of Tenant and determine Tenant's ability to fulfill its
                obligations under this Lease. Landlord, however, shall not
                require Tenant to provide such information unless Landlord is
                requested to produce the information in connection with a
                proposed financing or sale of the Building. Upon written request
                by Tenant, Landlord shall enter into a commercially reasonable
                confidentiality agreement covering any confidential information
                that is disclosed by Tenant.

        M.      Except with regard to requests for consent or approval that
                require Landlord to make a determination of the aesthetics of
                certain signage, alterations or other things that would be
                visible from outside the Premises or Building or to assume
                certain risks, including, without limitation, the risk that a
                certain alteration, addition and/or improvement could adversely
                affect the mechanical systems or structure of the Building or
                require excess removal costs, Landlord and Tenant agree to act
                reasonably in granting approval or disapproval of any requests
                by the other for consent or approval.

XXXII. ENTIRE AGREEMENT.

        This Lease and the following exhibits and attachments constitute the
entire agreement between the parties and supersede all prior agreements and
understandings related to the Premises, including all lease proposals, letters
of intent and other documents: ADDENDUM, EXHIBIT A-1 (Outline and Location of
Spear Premises), EXHIBIT A-2 (Outline and Location of Steuart Premises), EXHIBIT
A-3 (Outline and Location of Expansion Space), EXHIBIT A-4 (Legal Description of
Project), EXHIBIT B (Rules and Regulations), EXHIBIT C (Commencement Letter),
EXHIBIT D (Work Letter Agreement), EXHIBIT D-1 (Outline and Location of Bridge
Modifications), EXHIBIT E (Additional Provisions), EXHIBIT F (Parking
Agreement), EXHIBIT G (Form of Letter of Credit), EXHIBIT H (Form of Warrant
Agreement) and EXHIBIT I (Agreement of Subordination, Non-Disturber and
Attornment).

                                       28
<PAGE>   31

        Landlord and Tenant have executed this Lease as of the day and year
first above written.

                                       LANDLORD:

                                       EOP-ONE MARKET, L.L.C., A DELAWARE
                                       LIMITED LIABILITY COMPANY

                                       By:  EOP Operating Limited Partnership,
                                            a Delaware limited partnership, its
                                            sole member

                                            By:  Equity Office Properties Trust,
                                                 a Maryland real estate
                                                 investment trust, its managing
                                                 general partner

                                                 By:    /s/ PETER ADAMS
                                                        ------------------------
                                                 Name:  Peter Adams
                                                        ------------------------
                                                 Title: Senior Vice President
                                                        ------------------------

                                       TENANT:

                                       OMNISKY CORPORATION, A DELAWARE
                                       CORPORATION

                                       By:     /s/ LAWRENCE W. WINKLER
                                               -----------------------------
                                       Name:   Lawrence S. Winkler
                                               -----------------------------
                                       Title:  Chief Financial Officer
                                               -----------------------------

                                       By:     /s/ MICHAEL J. MALESARDI
                                               -----------------------------
                                       Name:   Michael J. Malesardi
                                               -----------------------------
                                       Title:  Controller
                                               -----------------------------

                                       29
<PAGE>   32

                                    ADDENDUM

        This Addendum is attached to and made a part of the Lease dated as of
the _____ day of _____________, 2000, by and between EOP-ONE MARKET, L.L.C., A
DELAWARE LIMITED LIABILITY COMPANY ("Landlord") and OMNISKY CORPORATION, A
DELAWARE CORPORATION ("Tenant") for space in the Spear Tower and the Steuart
Tower in the Building located at One Market, San Francisco, California.

                                   WITNESSETH:

        WHEREAS, simultaneously with the execution of this Addendum, Landlord
and Tenant have entered into that certain lease of even date herewith (the
"Lease") for approximately 35,982 rentable square feet on the 6th floor of the
Spear Tower and approximately 98,846 rentable square feet on the 3rd, 4th and
6th floors of the Steuart Tower, in the building located at One Market, San
Francisco, California (the "Building"), all as more particularly described in
the Lease; and

        WHEREAS, Landlord and Tenant desire to modify certain terms and
conditions of the Lease as set forth herein;

        NOW, THEREFORE, in consideration of the mutual covenants set forth
herein and other good and valuable consideration, the sufficiency and receipt of
which is acknowledged, Landlord and Tenant agree as follows:

1.      HAZARDOUS MATERIALS. Tenant shall not (either with or without
        negligence) cause or permit its agents or employees to permit the
        escape, disposal or release of any biologically or chemically active or
        other hazardous substances, or materials. Tenant shall not allow the
        storage or use of such substances or materials in any manner not
        sanctioned by law or by the highest standards prevailing in the industry
        for the storage and use of such substances of materials, nor allow to be
        brought into the Project any such materials or substances except to use
        for general office purposes in the ordinary course of Tenant's business,
        and then only after written notice is given to Landlord of the identity
        of such substances or materials. Without limitation, hazardous
        substances and materials shall include those described in the
        Comprehensive Environmental Response, Compensation and Liability Act of
        1980, as amended, 42 U.S.C. Section 9601 et seq., any applicable state
        or local laws and the regulations adopted under these acts. If any
        governmental agency or lender (in its reasonable judgment) shall ever
        require testing to ascertain whether or not there has been any release
        of hazardous materials, then the reasonable costs thereof shall be
        reimbursed by Tenant to Landlord upon demand as additional charges if
        such requirement applies to the Premises. In addition, Tenant shall
        execute affidavits, representations and the like from time to time at
        Landlord's request concerning Tenant's best knowledge and belief
        regarding the presence of hazardous substances or materials on the
        Premises. In all events, Tenant shall indemnify Landlord in the manner
        elsewhere provided in this Lease from any release of hazardous materials
        on the Premises occurring while Tenant is in possession (other than a
        release of hazardous materials in the Premises which is not caused by
        Tenant or persons acting under Tenant and which is brought about by the
        distribution of hazardous materials through the Building's mechanical
        systems), or elsewhere if caused by Tenant or persons acting under
        Tenant. In the event Tenant claims that the presence of hazardous
        materials in the Premises was caused by the distribution of hazardous
        materials through the Building's mechanical systems, the burden of
        showing the cause of the presence of such hazardous materials shall be
        borne by Tenant. The within covenants shall survive the expiration or
        earlier termination of the Term.

2.      SECURITY DEPOSIT. Notwithstanding anything in the Lease to the contrary,
        no purchaser of Landlord's interest in the Building or holder of any
        mortgage, deed of trust, ground lease or other lien on the Building
        shall be liable for the return of any Security Deposit unless and until
        such Security Deposit is actually transferred by Landlord to such party.

3.      NET INCOME/PROFITS. Notwithstanding anything contained to the contrary
        in the provisions of the Lease relating to an assignment or subletting
        by Tenant, neither Tenant nor any other person having an interest in the
        possession, use, occupancy or utilization of the Premises shall enter
        into any lease, sublease, license, concession or other agreement for
        use, occupancy or utilization of space in the Premises which

                                   ADDENDUM-1
<PAGE>   33

        provides for rental or other payment for such use, occupancy or
        utilization based, in whole or in part, on the net income or profits
        derived by any person from the portion of the Premises leased, used,
        occupied, or utilized (other than an amount based on a fixed percentage
        or percentages of receipts or sales), and any such purported lease,
        sublease, license, concession or other agreement shall be absolutely
        void and ineffective as a conveyance of any right or interest in the
        possession, use occupancy or utilization of any part of the Premises.

4.      CASUALTY/CONDEMNATION. Notwithstanding anything contained to the
        contrary in the Lease, the Premises or portion thereof shall not be
        considered to be untenantable or unusable by Tenant unless and until
        Tenant actually ceases to use the Premises or applicable portion
        thereof. In addition, the rights of Tenant, if any, to any condemnation
        proceeds and or insurance proceeds shall be subject and subordinate the
        rights of any party holding a first mortgage or first deed of trust on
        the Building. The foregoing, however, shall not be construed as to limit
        Tenant's right to receive the proceeds of any insurance policies
        maintained by Tenant at its sole cost and expense.

5.      LIMITATION OF LIABILITY. In addition to any limitation of Landlord's
        liability contained in the Lease, Tenant hereby agrees that any claim
        for damages against Landlord shall be subject and subordinate to the
        interest of any mortgagee in the Building and Project.

6.      ESTOPPEL CERTIFICATES. In addition to the obligations of Tenant under
        the Lease, Tenant agrees that it will from time to time upon request of
        Landlord, within 10 days after the date of such request, execute and
        deliver to such persons as Landlord shall request an estoppel
        certificate or other similar statement in recordable form certifying the
        following, to the extent true and accurate: (i) the Tenant is presently
        solvent and free from reorganization and/or bankruptcy and is in
        occupancy, open, and conducting business in the Premises, (ii) the
        operation and use of the Premises do not involve the generation,
        treatment, storage, etc. of hazardous substance etc., (iii) the rent is
        $___________ per year, (iv) the Lease represents the entire agreement
        between the parties (v) the expiration date is ___________, (vi) all
        conditions to be performed by the Landlord have been satisfied, (vii)
        all required contributions by Landlord to Tenant on account of Tenant
        improvements have been received, (viii) no rental has been paid more
        than one month in advance and no security has been deposited with
        Landlord except for $_______ and, (ix) the rentable square footage of
        the Premises is ________ square feet.

7.      SUBORDINATION TO MORTGAGES. Notwithstanding anything in the Lease to the
        contrary, the prior written consent of the holder of any first mortgage
        or first deed of trust on the Building shall be required as a condition
        precedent to the subordination of the Lease to any junior/secondary
        mortgage or deed of trust. In no event shall the holder of any first
        mortgage or first deed of trust be liable for any of Landlord's
        obligations under the Lease arising prior to the date such mortgagee or
        trustee takes title to the Building.

8.      CONFLICT. In the event of a conflict between the terms of this Addendum
        and the terms of the Lease or any exhibits thereto, the terms of this
        Addendum shall control.

                                   ADDENDUM-2
<PAGE>   34

        IN WITNESS WHEREOF, Landlord and Tenant have executed this Addendum on
the day and year first above written.

                                       LANDLORD:

                                       EOP-ONE MARKET, L.L.C., A DELAWARE
                                       LIMITED LIABILITY COMPANY

                                       By:  EOP Operating Limited Partnership,
                                            a Delaware limited partnership, its
                                            sole member

                                            By:  Equity Office Properties Trust,
                                                 a Maryland real estate
                                                 investment trust,its managing
                                                 general partner

                                                 By:    ________________________

                                                 Name:  ________________________

                                                 Title: ________________________

                                       TENANT:

                                       OMNISKY CORPORATION, A DELAWARE
                                       CORPORATION

                                       By:     _____________________________
                                       Name:   _____________________________
                                       Title:  _____________________________

                                       By:     _____________________________
                                       Name:   _____________________________
                                       Title:  _____________________________

                                   ADDENDUM-3
<PAGE>   35

                                   EXHIBIT A-1

                     OUTLINE AND LOCATION OF SPEAR PREMISES

        This Exhibit is attached to and made a part of the Lease dated as of the
____ day of _____________, 2000, by and between EOP-ONE MARKET, L.L.C., A
DELAWARE LIMITED LIABILITY COMPANY ("Landlord") and OMNISKY CORPORATION, A
DELAWARE CORPORATION ("Tenant") for space in the Spear Tower and the Steuart
Tower in the Building located at One Market, San Francisco, California.

                                      A-1
<PAGE>   36

                                   EXHIBIT A-2

                    OUTLINE AND LOCATION OF STEUART PREMISES

        This Exhibit is attached to and made a part of the Lease dated as of the
____ day of _____________, 2000, by and between EOP-ONE MARKET, L.L.C., A
DELAWARE LIMITED LIABILITY COMPANY ("Landlord") and OMNISKY CORPORATION, A
DELAWARE CORPORATION ("Tenant") for space in the Spear Tower and the Steuart
Tower in the Building located at One Market, San Francisco, California.

                                      A-2
<PAGE>   37

                                   EXHIBIT A-3

                     OUTLINE AND LOCATION OF EXPANSION SPACE

This Exhibit is attached to and made a part of the Lease dated as of the ____
day of _____________, 2000, by and between EOP-ONE MARKET, L.L.C., A DELAWARE
LIMITED LIABILITY COMPANY ("Landlord") and OMNISKY CORPORATION, A DELAWARE
CORPORATION ("Tenant") for space in the Spear Tower and the Steuart Tower in the
Building located at One Market, San Francisco, California.

                                      A-3
<PAGE>   38

                                   EXHIBIT A-4

                          LEGAL DESCRIPTION OF PROJECT

THE LAND REFERRED TO HEREIN IS SITUATED IN THE STATE OF CALIFORNIA, COUNTY OF
SAN FRANCISCO, CITY OF SAN FRANCISCO, AND IS DESCRIBED AS FOLLOWS:

BEGINNING AT THE POINT OF INTERSECTION OF THE NORTHWESTERLY LINE OF MISSION
STREET WITH THE SOUTHWESTERLY LINE OF STEUART STREET; THENCE NORTH 44 DEGREES
51' 51" WEST ALONG SAID SOUTHWESTERLY LINE, 334.33 FEET TO A POINT IN A LINE
PARALLEL WITH AND DISTANT 334.33 FEET NORTHWESTERLY, MEASURED AT RIGHT ANGLES,
FROM SAID NORTHWESTERLY LINE OF MISSION STREET; THENCE SOUTH 45 DEGREES 08' 09"
WEST ALONG SAID PARALLEL LINE 32 FEET AND 4-1/2 INCHES; THENCE NORTH 44 DEGREES
51' 51" WEST 6 FEET AND 1-1/2 INCHES; THENCE SOUTH 45 DEGREES 08' 09" WEST 16
FEET AND 4 INCHES; THENCE NORTH 44 DEGREES 51' 51" WEST 112 FEET AND 5-1/8
INCHES; THENCE SOUTH 45 DEGREES 08' 09" WEST 177 FEET AND 7-1/2 INCHES; THENCE
SOUTH 44 DEGREES 51' 51" EAST 112 FEET AND 5-1/8 INCHES; THENCE SOUTH 45 DEGREES
08' 09" WEST 16 FEET AND 3-1/2 INCHES; THENCE SOUTH 44 DEGREES 51' 51" EAST 6
FEET AND 1-1/2 INCHES TO A POINT IN SAID PARALLEL LINE; THENCE SOUTH 45 DEGREES
09' 09" WEST ALONG SAID PARALLEL LINE 32 FEET AND 4-1/2 INCHES TO A POINT IN THE
NORTHEASTERLY LINE OF SPEAR STREET; THENCE SOUTH 44 DEGREES 51' 51" EAST ALONG
SAID NORTHEASTERLY LINE, 334.33 FEET TO A POINT IN SAID NORTHWESTERLY LINE OF
MISSION STREET; THENCE NORTH 45 DEGREES 08' 09" EAST ALONG SAID NORTHWESTERLY
LINE 274 FEET TO THE POINT OF BEGINNING.

                                      A-4
<PAGE>   39

                                    EXHIBIT B

                         BUILDING RULES AND REGULATIONS

        The following rules and regulations shall apply, where applicable, to
the Premises, the Building, the parking garage (if any), the Project and the
appurtenances. Capitalized terms have the same meaning as defined in the Lease.

1.      Sidewalks, doorways, vestibules, halls, stairways and other similar
        areas shall not be obstructed by Tenant or used by Tenant for any
        purpose other than ingress and egress to and from the Premises. No
        rubbish, litter, trash, or material shall be placed, emptied, or thrown
        in those areas. At no time shall Tenant permit Tenant's employees to
        loiter in Common Areas or elsewhere about the Building or Project.

2.      Plumbing fixtures and appliances shall be used only for the purposes for
        which designed, and no sweepings, rubbish, rags or other unsuitable
        material shall be thrown or placed in the fixtures or appliances. Damage
        resulting to fixtures or appliances by Tenant, its agents, employees or
        invitees, shall be paid for by Tenant, and Landlord shall not be
        responsible for the damage.

3.      No signs, advertisements or notices shall be painted or affixed to
        windows, doors or other parts of the Building, except those of such
        color, size, style and in such places as are first approved in writing
        by Landlord. All tenant identification and suite numbers at the entrance
        to the Premises shall be installed by Landlord, at Tenant's cost and
        expense, using the standard graphics for the Building. Except in
        connection with the hanging of lightweight pictures and wall
        decorations, no nails, hooks or screws shall be inserted into any part
        of the Premises or Building except by the Building maintenance
        personnel. Notwithstanding the foregoing, Tenant shall have the right to
        elevator lobby signage on each floor on which Tenant occupies the entire
        floor.

4.      Landlord shall provide and maintain in the first floor (main lobby) of
        the Building an alphabetical directory board or other directory device
        listing tenants, and no other directory shall be permitted unless
        previously consented to by Landlord in writing. So long as Landlord
        maintains the same in the main lobby of the Building, Tenant shall have
        the right to utilize one line on the non-electronic lobby directory
        board, and Tenant shall have the right to utilize multiple lines on the
        electronic lobby directory board (the exact number of such multiple
        lines to be reasonably determined by Landlord taking into account the
        capacity of the electronic lobby directory board).

5.      Tenant shall not place any lock(s) on any door in the Premises or
        Building without Landlord's prior written consent and Landlord shall
        have the right to retain at all times and to use keys to all locks
        within and into the Premises. A reasonable number of keys to the locks
        on the entry doors in the Premises shall be furnished by Landlord to
        Tenant at Tenant's cost, and Tenant shall not make any duplicate keys.
        All keys shall be returned to Landlord at the expiration or early
        termination of this Lease.

6.      All contractors, contractor's representatives and installation
        technicians performing work in the Building shall be subject to
        Landlord's prior approval and shall be required to comply with
        Landlord's standard rules, regulations, policies and procedures, which
        may be revised from time to time.

7.      Movement in or out of the Building of furniture or office equipment, or
        dispatch or receipt by Tenant of merchandise or materials requiring the
        use of elevators, stairways, lobby areas or loading dock areas, shall be
        restricted to hours designated by Landlord. Tenant shall obtain
        Landlord's prior approval by providing a detailed listing of the
        activity. If approved by Landlord, the activity shall be under the
        supervision of Landlord and performed in the manner required by
        Landlord. Tenant shall assume all risk for damage to articles moved and
        injury to any persons resulting from the activity. If equipment,
        property, or personnel of Landlord or of any other party is damaged or
        injured as a result of or in connection with the activity, Tenant shall
        be solely liable for any resulting damage or loss.

8.      Landlord shall have the right to approve the weight, size, or location
        of heavy equipment or articles in and about the Premises. Damage to the
        Building by the installation,

                                       B-1
<PAGE>   40

        maintenance, operation, existence or removal of Tenant's Property shall
        be repaired at Tenant's sole expense.

9.      Corridor doors, when not in use, shall be kept closed.

10.     Tenant shall not: (1) make or permit any improper, objectionable or
        unpleasant noises or odors in the Building, or otherwise interfere in
        any way with other tenants or persons having business with them; (2)
        solicit business or distribute, or cause to be distributed, in any
        portion of the Building, handbills, promotional materials or other
        advertising; or (3) conduct or permit other activities in the Building
        that might, in Landlord's sole opinion, constitute a nuisance.

11.     No animals, except those assisting handicapped persons, shall be brought
        into the Building or kept in or about the Premises.

12.     No inflammable, explosive or dangerous fluids or substances shall be
        used or kept by Tenant in the Premises, Building or about the Project.
        Tenant shall not, without Landlord's prior written consent, use, store,
        install, spill, remove, release or dispose of, within or about the
        Premises or any other portion of the Project, any asbestos-containing
        materials or any solid, liquid or gaseous material now or subsequently
        considered toxic or hazardous under the provisions of 42 U.S.C. Section
        9601 et seq. or any other applicable environmental Law which may now or
        later be in effect. Tenant shall comply with all Laws pertaining to and
        governing the use of these materials by Tenant, and shall remain solely
        liable for the costs of abatement and removal.

13.     Tenant shall not use or occupy the Premises in any manner or for any
        purpose which might injure the reputation or impair the present or
        future value of the Premises or the Building. Tenant shall not use, or
        permit any part of the Premises to be used, for lodging, sleeping or for
        any illegal purpose.

14.     Tenant shall not take any action which would violate Landlord's labor
        contracts or which would cause a work stoppage, picketing, labor
        disruption or dispute, or interfere with Landlord's or any other
        tenant's or occupant's business or with the rights and privileges of any
        person lawfully in the Building ("Labor Disruption"). Tenant shall take
        the actions necessary to resolve the Labor Disruption, and shall have
        pickets removed and, at the request of Landlord, immediately terminate
        any work in the Premises that gave rise to the Labor Disruption, until
        Landlord gives its written consent for the work to resume. Tenant shall
        have no claim for damages against Landlord or any of the Landlord
        Related Parties, nor shall the Commencement Date of the Term be extended
        as a result of the above actions.

15.     Tenant shall not install, operate or maintain in the Premises or in any
        other area of the Building, electrical equipment that would overload the
        electrical system beyond its capacity for proper, efficient and safe
        operation as determined solely by Landlord. Tenant shall not furnish
        cooling or heating to the Premises, including, without limitation, the
        use of electronic or gas heating devices, without Landlord's prior
        written consent. Tenant shall not use more than its proportionate share
        of telephone lines and other telecommunication facilities available to
        service the Building.

16.     Tenant shall not operate or permit to be operated a coin or token
        operated vending machine or similar device (including, without
        limitation, telephones, lockers, toilets, scales, amusement devices and
        machines for sale of beverages, foods, candy, cigarettes and other
        goods), except for machines for the exclusive use of Tenant's employees,
        and then only if the operation does not violate the lease of any other
        tenant in the Building.

17.     Bicycles and other vehicles are not permitted inside the Building or on
        the walkways outside the Building, except in areas designated by
        Landlord. Landlord acknowledges that Landlord has, as of the date of
        this Lease, designated certain areas as bicycle parking areas in the
        basement of the Building.

18.     Landlord may from time to time adopt systems and procedures for the
        security and safety of the Building, its occupants, entry, use and
        contents. Tenant, its agents, employees, contractors, guests and
        invitees shall comply with Landlord's systems and procedures.

                                      B-2
<PAGE>   41

19.     Landlord shall have the right to prohibit the use of the name of the
        Building or any other publicity by Tenant that in Landlord's sole
        opinion may impair the reputation of the Building or its desirability.
        Upon written notice from Landlord, Tenant shall refrain from and
        discontinue such publicity immediately.

20.     Tenant shall not canvass, solicit or peddle in or about the Building or
        the Project.

21.     Neither Tenant nor its agents, employees, contractors, guests or
        invitees shall smoke or permit smoking in the Common Areas, unless the
        Common Areas have been declared a designated smoking area by Landlord,
        nor shall the above parties allow smoke from the Premises to emanate
        into the Common Areas or any other part of the Building. Landlord shall
        have the right to designate the Building (including the Premises) as a
        non-smoking building.

22.     Landlord shall have the right to designate and approve standard window
        coverings for the Premises and to establish rules to assure that the
        Building presents a uniform exterior appearance. Tenant shall ensure, to
        the extent reasonably practicable, that window coverings are closed on
        windows in the Premises while they are exposed to the direct rays of the
        sun.

23.     Deliveries to and from the Premises shall be made only at the times, in
        the areas and through the entrances and exits designated by Landlord.
        Tenant shall not make deliveries to or from the Premises in a manner
        that might interfere with the use by any other tenant of its premises or
        of the Common Areas, any pedestrian use, or any use which is
        inconsistent with good business practice.

24.     The work of cleaning personnel shall not be hindered by Tenant after
        5:30 P.M., and cleaning work may be done at any time when the offices
        are vacant. Windows, doors and fixtures may be cleaned at any time.
        Tenant shall provide adequate waste and rubbish receptacles to prevent
        unreasonable hardship to the cleaning service.

                                      B-3
<PAGE>   42

                                    EXHIBIT C

                               COMMENCEMENT LETTER
                                    (EXAMPLE)

Date           ______________________

Tenant         OmniSky Corporation
Address        ______________________

               ______________________

               ______________________

Re:     Commencement Letter with respect to that certain Lease dated as of the
        _____ day of __________, 2000, by and between EOP-ONE MARKET, L.L.C., A
        DELAWARE LIMITED LIABILITY COMPANY, as Landlord, and OMNISKY
        CORPORATION, A DELAWARE CORPORATION, as Tenant, for ________ rentable
        square feet on the ___ floor of _____ Tower in the Building located at
        One Market, San Francisco, California.

Dear    __________________:

        In accordance with the terms and conditions of the above referenced
Lease, Tenant accepts possession of the _____________ Premises and agrees:

        1.      The _______________ Commencement Date is ______________________.

        2.      The Termination Date of the Lease is __________________________.

        3.      The Base Rent schedule for the ___________ Premises set forth in
                Section I.D. of the Lease is restated as follows:

                        BASE RENT FOR __________ PREMISES

<TABLE>
<CAPTION>
                                          ANNUAL RATE            ANNUAL            MONTHLY
                      PERIOD            PER SQUARE FOOT         BASE RENT         BASE RENT
                      ------            ---------------         ---------         ---------
                      <S>               <C>                     <C>               <C>

</TABLE>

        Please acknowledge your acceptance of possession and agreement to the
terms set forth above by signing all 4 counterparts of this Commencement Letter
in the space provided and returning all executed counterparts to Landlord.

                                       C-1
<PAGE>   43

        IN WITNESS WHEREOF, Landlord and Tenant have executed this Commencement
Letter as of the day and year first above written.

                                       LANDLORD:

                                       EOP-ONE MARKET, L.L.C., A DELAWARE
                                       LIMITED LIABILITY COMPANY

                                       By:  EOP Operating Limited Partnership,
                                            a Delaware limited partnership, its
                                            agent

                                            By:    __________________________

                                            Name:  __________________________

                                            Title: __________________________

                                       TENANT:

                                       OMNISKY CORPORATION, A DELAWARE
                                       CORPORATION

                                       By:     _____________________________
                                       Name:   _____________________________
                                       Title:  _____________________________

                                       By:     _____________________________
                                       Name:   _____________________________
                                       Title:  _____________________________

                                      C-2
<PAGE>   44

                                    EXHIBIT D

                                   WORK LETTER

        This Exhibit is attached to and made a part of the Lease dated as of the
____ day of _____________, 2000, by and between EOP-ONE MARKET, L.L.C., A
DELAWARE LIMITED LIABILITY COMPANY ("Landlord") and OMNISKY CORPORATION, A
DELAWARE CORPORATION ("Tenant") for space in the Spear Tower and the Steuart
Tower in the Building located at One Market, San Francisco, California.

I.      ALTERATIONS AND ALLOWANCE.

        A.      Tenant, immediately following the delivery of the Premises by
                Landlord and the full and final execution and delivery of this
                Lease and all prepaid rental and security deposits required
                hereunder, shall have the right to perform alterations and
                improvements in the Premises (the "Initial Alterations"). For
                purposes of this Lease, the parties hereto agree that in the
                event Tenant subleases the 4th Floor Steuart Premises and such
                sublease is consented to by Landlord (if required), the Initial
                Alterations shall be deemed to include those alterations made to
                the 4th Floor Steuart Premises subsequent to the expiration of
                the proposed sublease, provided that any such alterations are
                made by Tenant within 4 years of the 4th Floor Steuart Premises
                Commencement Date. Notwithstanding the foregoing, Tenant and its
                contractors shall not have the right to perform Initial
                Alterations in the Premises unless and until Tenant has complied
                with all of the terms and conditions of Article IX.C. of this
                Lease, including, without limitation, approval by Landlord of
                the final plans for the Initial Alterations and the contractors
                to be retained by Tenant to perform such Initial Alterations.
                Tenant shall be responsible for all elements of the design of
                Tenant's plans for the Initial Alterations (including, without
                limitation, compliance with law, functionality of design, the
                structural integrity of the design, the configuration of the
                Premises and the placement of Tenant's furniture, appliances and
                equipment), and Landlord's approval of Tenant's plans shall in
                no event relieve Tenant of the responsibility for such design.
                Landlord's approval of the contractors to perform the Initial
                Alterations shall not be unreasonably withheld. The parties
                agree that Landlord's approval of the general contractor to
                perform the Initial Alterations shall not be considered to be
                unreasonably withheld if any such general contractor (i) does
                not have trade references reasonably acceptable to Landlord,
                (ii) does not maintain insurance as required pursuant to the
                terms of this Lease, (iii) does not have the ability to be
                bonded for the work in an amount of no less than $2,000,000.00,
                (iv) does not provide current financial statements reasonably
                acceptable to Landlord, or (v) is not licensed as a contractor
                in the state/municipality in which the Premises is located.
                Tenant acknowledges the foregoing is not intended to be an
                exclusive list of the reasons why Landlord may reasonably
                withhold its consent to a general contractor. Tenant shall be
                required to use Glumac International for all engineering work to
                be performed in the Premises. In addition, Tenant shall be
                required to use Siemens Building Technologies, Inc. as the fire,
                life and safety subcontractor for all fire, life and safety work
                to be performed in the Premises. Notwithstanding the foregoing
                to the contrary, Tenant shall be permitted to use a contractor
                other than Glumac International for the engineering work with
                respect to the Initial Alterations provided that (i) such
                alternative engineering contractor is acceptable to Landlord in
                Landlord's sole discretion, (ii) any engineering work performed
                by such alternative engineering contractor is subject to the
                prior review and approval of such work by Glumac International
                (and in the event any such work is not acceptable to Glumac
                International, the alternative engineering contractor shall make
                such changes as are required by Glumac International), and (iii)
                Tenant pays to Glumac International, in addition to any amounts
                due and payable to such alternative engineering contractor, the
                applicable fee charged by Glumac International for its
                performance of the oversight and review work.

        B.      Provided Tenant is not in default beyond the expiration of
                applicable notice and cure periods (if any), Landlord agrees to
                contribute the sum of (i) $1,118,293.00 (the "Allowance") toward
                the cost of performing the Initial Alterations in preparation

                                       D-1
<PAGE>   45

                of Tenant's occupancy of the Premises. Landlord shall be
                entitled to deduct from the Allowance a construction management
                fee for Landlord's oversight of the Initial Alterations in the
                amount of 3% of the total cost of the Initial Alterations. The
                Allowance may only be used for the cost of preparing design and
                construction documents and mechanical and electrical plans for
                the Initial Alterations, permitting costs and for hard costs in
                connection with the Initial Alterations. The Allowance, less a
                10% retainage (which retainage shall be payable as part of the
                final draw) shall be paid to Tenant or, at Landlord's option, to
                the order of the general contractor that performs the Initial
                Alterations, in periodic disbursements within 30 days after
                receipt of the following documentation: (i) an application for
                payment and sworn statement of the general contractor
                substantially in the form of AIA Document G-702 covering all
                work for which disbursement is to be made to a date specified
                therein; (ii) a certification from an AIA architect
                substantially in the form of the Architect's Certificate for
                Payment which is located on AIA Document G702, Application and
                Certificate of Payment; (iii) contractor's, subcontractor's and
                material supplier's waivers of liens which shall cover all
                Initial Alterations for which disbursement is being requested
                and all other statements and forms required for compliance with
                the mechanics' lien laws of the State of California, together
                with all such invoices, contracts, or other supporting data as
                Landlord or Landlord's Mortgagee may reasonably require; (iv) a
                cost breakdown for each trade or subcontractor performing the
                Initial Alterations; (v) plans and specifications for the
                Initial Alterations, together with a certificate from an AIA
                architect that such plans and specifications comply in all
                material respects with all Laws affecting the Building, Property
                and Premises; (vi) copies of all construction contracts for the
                Initial Alterations, together with copies of all change orders,
                if any; and (vii) a request to disburse from Tenant containing
                an approval by Tenant of the work done and a good faith estimate
                of the cost to complete the Initial Alterations. Upon completion
                of the Initial Alterations, and prior to final disbursement of
                the Allowance, Tenant shall furnish Landlord with: (1) general
                contractor and architect's completion affidavits, (2) full and
                final waivers of lien, (3) receipted bills covering all labor
                and materials expended and used, (4) as-built plans of the
                Initial Alterations, and (5) the certification of Tenant and its
                architect that the Initial Alterations have been installed in a
                good and workmanlike manner in accordance with the approved
                plans, and in accordance with applicable laws, codes and
                ordinances. In no event shall Landlord be required to disburse
                the Allowance more than one time per month. If the Initial
                Alterations exceed the Allowance, Tenant shall be entitled to
                the Allowance in accordance with the terms hereof, but each
                individual disbursement of the Allowance shall be disbursed in
                the proportion that the Allowance bears to the total cost for
                the Initial Alterations, less the 10% retainage referenced
                above. Notwithstanding anything herein to the contrary, Landlord
                shall not be obligated to disburse any portion of the Allowance
                during the continuance of an uncured default under the Lease
                after the expiration of applicable notice and cure periods (if
                any), and Landlord's obligation to disburse shall only resume
                when and if such default is cured.

        C.      In no event shall the Allowance be used for the purchase of
                equipment, furniture or other items of personal property of
                Tenant. In the event Tenant does not use the entire Allowance
                within 12 months from the Final Commencement Date, any unused
                amount shall accrue to the sole benefit of Landlord, it being
                understood that Tenant shall not be entitled to any credit,
                abatement or other concession in connection therewith. Tenant
                shall be responsible for all applicable state sales or use
                taxes, if any, payable in connection with the Initial
                Alterations and/or Allowance.

        D.      Except as expressly set forth herein, Tenant agrees to accept
                the Premises in its "as-is" condition and configuration, it
                being agreed that Landlord shall not be required to perform any
                work or, except as provided above with respect to the Allowance,
                incur any costs in connection with the construction or
                demolition of any improvements in the Premises. Notwithstanding
                any of the foregoing to the contrary, Landlord shall be
                responsible for performing Building standard modifications to
                the restrooms within the core area of the Premises in accordance
                with plans and specifications to be prepared by Landlord, in
                order to comply with Title 24 and the American with Disabilities
                Act and any other applicable Laws (collectively, the "ADA
                Modifications"). Landlord and Tenant acknowledge and agree that
                in the event Tenant subleases all or a portion of the

                                      D-2
<PAGE>   46

                4th Floor Steuart Premises, the ADA Modifications may be
                performed by Landlord during the occupancy of such subtenant
                during or after Normal Business Hours. In such event, Landlord
                shall have no liability for any loss, damage, claim or injury
                suffered or incurred by Tenant, its subtenant or any of their
                respective agents, contractors or employees as a result of the
                performance of such work, and Tenant shall be entitled to no
                credit, abatement or adjustment of Rent or other sums payable
                under this Lease. In the alternative, Tenant may request by
                written notice to Landlord received within 5 Business Days of
                the date of this Lease, that Landlord not perform the ADA
                Modifications in the 4th Floor Steuart Premises. In such event,
                Landlord shall have no further obligation to perform the ADA
                Modifications in the 4th Floor Steuart Premises, and Tenant
                shall be solely responsible for the compliance of all Laws,
                including the Americans with Disabilities Act, regarding the
                use, condition, configuration and occupancy of the bathrooms in
                the 4th Floor Steuart Premises. The ADA Modifications shall
                include modifications necessary to comply with path of travel
                requirements of the ADA within the bathrooms located in the
                Premises. Landlord's obligations with respect to the bathrooms
                in the Premises shall be limited to the obligation to ensure
                that such bathrooms are in compliance with all applicable Laws
                as of the applicable Commencement Date for such applicable
                portion of the Premises, and Tenant shall have the sole
                obligation to correct any non-compliance of Laws with respect to
                the bathrooms in the Premises after the applicable Commencement
                Date. Notwithstanding the foregoing to the contrary, Landlord
                shall have no obligation to ensure that the bathrooms in the 4th
                Floor Steuart Premises comply with all applicable Laws in the
                event Tenant requests that Landlord not perform the ADA
                Modifications in the 4th Floor Steuart Premises as provided
                above. In addition to Landlord's obligation with respect to the
                ADA Modifications, Landlord shall also be responsible for
                performing certain work (the "Bridge Modifications") consisting
                of the construction of a corridor of approximately 5-6 feet in
                width in the north bridge connecting the 6th Floor Steuart
                Premises with the Spear Premises. The Bridge Modifications are
                more fully set forth on EXHIBIT D-1 attached to this Lease.
                Tenant shall have no right to review or approve of Landlord's
                plans for the ADA Modifications or the Bridge Modifications
                except that Tenant shall have the right to select the applicable
                Building standard finishes for the ADA Modifications provided
                that Tenant makes such selection within 3 Business Days after
                request from Landlord. Except for the ADA Modifications, the
                restrooms shall be delivered to Tenant by Landlord in their "as
                is" condition. Tenant acknowledges that the improvements to the
                ADA Modifications and the Bridge Modifications will be performed
                by Landlord on or about the same time that the Initial
                Alterations will be performed by Tenant. Landlord shall perform
                the ADA Modifications and the Bridge Modifications in a good and
                workmanlike manner, in compliance with all Laws and the approved
                plans. Landlord and Tenant agree to cooperate with each other in
                order to enable the ADA Modifications, the Bridge Modifications
                and the Initial Alterations to be performed in a timely manner
                and with as little inconvenience to the work of the other party
                hereto as is reasonably possible. Notwithstanding anything
                herein to the contrary, any delay in the completion of the
                Initial Alterations or inconvenience suffered by Tenant during
                the performance of the ADA Modifications or the Bridge
                Modifications shall not subject Landlord to any liability for
                any loss or damage resulting therefrom or entitle Tenant to any
                credit, abatement or adjustment of Rent or other sums payable
                under the Lease. Furthermore, if Landlord is delayed in the
                performance of the ADA Modifications or the Bridge Modifications
                as a result of any Tenant Delay(s) (defined below), the ADA
                Modifications or the Bridge Modifications, as the case may be,
                shall be deemed to be "Substantially Complete" on the date that
                Landlord could reasonably have been expected to Substantially
                Complete the ADA Modifications or the Bridge Modifications, as
                the case may be, absent any Tenant Delay. "Tenant Delay" means
                any act or omission of Tenant or its agents, employees, vendors
                or contractors that actually delays the Substantial Completion
                of the ADA Modifications or the Bridge Modifications, including,
                without limitation: (1) Tenant's failure to furnish information
                or approvals within any time period specified in this Lease,
                including the failure to choose the applicable Building standard
                finishes for the ADA Modifications within 3 Business Days after
                request from Landlord; (2) performance of work in the Premises
                by Tenant or Tenant's contractor(s) during the performance of
                the ADA Modifications or the Bridge Modifications which would
                materially interfere with

                                      D-3
<PAGE>   47

                Landlord's performance of the ADA Modifications or the Bridge
                Modifications; or (3) if the performance of any portion of the
                ADA Modifications or the Bridge Modifications depend on the
                prior or simultaneous performance of work by Tenant, a delay by
                Tenant or Tenant's contractor(s) in the completion of such work.

        E.      This EXHIBIT D shall not be deemed applicable to any additional
                space added to the original Premises at any time or from time to
                time, whether by any options under the Lease or otherwise, or to
                any portion of the original Premises or any additions to the
                Premises in the event of a renewal or extension of the original
                Term of this Lease, whether by any options under the Lease or
                otherwise, unless expressly so provided in the Lease or any
                amendment or supplement to the Lease.

        Landlord and Tenant have executed this exhibit as of the day and year
first above written.

                                       LANDLORD:

                                       EOP-ONE MARKET, L.L.C., A DELAWARE
                                       LIMITED LIABILITY COMPANY

                                       By:  EOP Operating Limited Partnership,
                                            a Delaware limited partnership, its
                                            sole member

                                            By:  Equity Office Properties Trust,
                                                 a Maryland real estate
                                                 investment trust, its managing
                                                 general partner

                                                 By:    ________________________

                                                 Name:  ________________________

                                                 Title: ________________________

                                       TENANT:

                                       OMNISKY CORPORATION, A DELAWARE
                                       CORPORATION

                                       By:     _____________________________
                                       Name:   _____________________________
                                       Title:  _____________________________

                                       By:     _____________________________
                                       Name:   _____________________________
                                       Title:  _____________________________

                                      D-4
<PAGE>   48

                                   EXHIBIT D-1

                  OUTLINE AND LOCATION OF BRIDGE MODIFICATIONS

                                       E-1
<PAGE>   49

                                    EXHIBIT E

                              ADDITIONAL PROVISIONS

        This Exhibit is attached to and made a part of the Lease dated as of the
____ day of _____________, 2000, by and between EOP-ONE MARKET, L.L.C., A
DELAWARE LIMITED LIABILITY COMPANY ("Landlord") and OMNISKY CORPORATION, A
DELAWARE CORPORATION ("Tenant") for space in the Spear Tower and the Steuart
Tower in the Building located at One Market, San Francisco, California.

I.      RENEWAL OPTION.

        A.      Tenant shall have the right to extend the Term (the "Renewal
                Option") for one additional period of 5 years commencing on the
                day following the Termination Date of the initial Term and
                ending on the 5th anniversary of the Termination Date (the
                "Renewal Term"), if:

                1.      Landlord receives notice of exercise of the Renewal
                        Option ("Initial Renewal Notice") not less than 9 full
                        calendar months prior to the expiration of the initial
                        Term and not more than 12 full calendar months prior to
                        the expiration of the initial Term; and

                2.      Tenant is not in Monetary Default or material
                        non-monetary default under the Lease beyond any
                        applicable cure periods at the time that Tenant delivers
                        its Initial Renewal Notice or at the time Tenant
                        delivers its Binding Notice (as hereinafter defined);
                        and

                3.      No more than 16,500 rentable square feet of the Premises
                        (in the aggregate) is sublet (other than pursuant to a
                        Permitted Transfer) at the time that Tenant delivers its
                        Initial Renewal Notice or at the time Tenant delivers
                        its Binding Notice; and

                4.      The Lease has not been assigned (other than pursuant to
                        a Permitted Transfer) prior to the date that Tenant
                        delivers its Initial Renewal Notice or prior to the date
                        Tenant delivers its Binding Notice.

        B.      The initial Base Rent rate per rentable square foot for the
                Premises during the Renewal Term shall equal the Prevailing
                Market (hereinafter defined) rate per rentable square foot for
                the Premises.

        C.      Tenant shall pay Additional Rent (i.e. Expenses and Taxes) for
                the Premises during the Renewal Term in accordance with Article
                IV of the Lease, provided that the Base Year for Expenses and
                the Base Year for Taxes during the Renewal Term shall be the
                calendar year during which the Renewal Term commences.

        D.      Within 30 days after receipt of Tenant's Initial Renewal Notice,
                Landlord shall advise Tenant of the applicable Base Rent rate
                for the Premises for the Renewal Term. Tenant, within 15 days
                after the date on which Landlord advises Tenant of the
                applicable Base Rent rate for the Renewal Term, shall either (i)
                give Landlord final binding written notice ("Binding Notice") of
                Tenant's exercise of its option, or (ii) if Tenant disagrees
                with Landlord's determination, provide Landlord with written
                notice of rejection (the "Rejection Notice"). If Tenant fails to
                provide Landlord with either a Binding Notice or Rejection
                Notice within such 15 day period, Tenant's Renewal Option shall
                be null and void and of no further force and effect. If Tenant
                provides Landlord with a Binding Notice, Landlord and Tenant
                shall enter into the Renewal Amendment upon the terms and
                conditions set forth herein. If Tenant provides Landlord with a
                Rejection Notice, Landlord and Tenant shall work together in
                good faith to agree upon the Prevailing Market Base Rent rate
                for the Premises during the Renewal Term. Upon agreement Tenant
                shall provide Landlord with Binding Notice and Landlord and
                Tenant shall enter into the Renewal Amendment in accordance with
                the terms and conditions hereof. Notwithstanding the foregoing,
                if Landlord and Tenant are unable to agree upon the Prevailing
                Market Base Rent rate for the Premises within 30 days

                                      E-2
<PAGE>   50

                after the date on which Tenant provides Landlord with a
                Rejection Notice, Tenant may elect to either rescind its
                intention to renew, or subject the process to binding
                arbitration. Tenant's election to cause the disagreement to be
                resolved by arbitration shall be deemed to be its Binding
                Notice. If Tenant fails to require arbitration by notice (the
                "Renewal Arbitration Notice") within 5 days of the expiration of
                the 30 day period set forth above, Tenant's right to extend the
                Lease shall be null and void and of no further force and effect.

                If Tenant timely provides Landlord with an Renewal Arbitration
                Notice, Landlord and Tenant, within 10 days after the date of
                the Renewal Arbitration Notice, shall each simultaneously submit
                to the other, in a sealed envelope, its good faith estimate of
                the Prevailing Market Base Rent rate (collectively referred to
                as the "Renewal Estimates"). If the higher of such Renewal
                Estimates is not more than 105% of the lower of such Renewal
                Estimates, then Prevailing Market Base Rent rate shall be the
                average of the 2 Renewal Estimates. If the Prevailing Market
                Base Rent rate is not resolved by the exchange of Renewal
                Estimates, Landlord and Tenant, within 7 days after the exchange
                of Renewal Estimates, shall each select an appraiser to
                determine which of the 2 Renewal Estimates most closely reflects
                the Prevailing Market Base Rent rate for the Premises during the
                Renewal Term. Each appraiser so selected shall be certified as
                an MAI appraiser or as an ASA appraiser and shall have had at
                least 5 years experience within the previous 10 years as a real
                estate appraiser working in the downtown San Francisco,
                California area, with working knowledge of current rental rates
                and practices. For purposes of this Lease, an "MAI" appraiser
                means an individual who holds an MAI designation conferred by,
                and is an independent member of, the American Institute of Real
                Estate Appraisers (or its successor organization, or in the
                event there is no successor organization, the organization and
                designation most similar), and an "ASA" appraiser means an
                individual who holds the Senior Member designation conferred by,
                and is an independent member of, the American Society of
                Appraisers (or its successor organization, or, in the event
                there is no successor organization, the organization and
                designation most similar). Upon selection, Landlord's and
                Tenant's appraisers shall work together in good faith to agree
                upon which of the 2 Renewal Estimates most closely reflects the
                Prevailing Market Base Rent rate for the Premises during the
                Renewal Term. The Renewal Estimate chosen by such appraisers
                shall be binding on both Landlord and Tenant as the Base Rent
                rate for the Premises during the Renewal Term. If either
                Landlord or Tenant fails to appoint an appraiser within the 7
                day period referred to above, the appraiser appointed by the
                other party shall be the sole appraiser for the purposes hereof.
                If the 2 appraisers cannot agree upon which of the 2 Renewal
                Estimates most closely reflects the Prevailing Market within the
                20 days after their appointment, then, within 10 days after the
                expiration of such 20 day period, the 2 appraisers shall select
                a third appraiser meeting the aforementioned criteria. Once the
                third appraiser has been selected as provided for above, then,
                as soon thereafter as practicable but in any case within 14
                days, the third appraiser shall make his determination of which
                of the 2 Renewal Estimates most closely reflects the Prevailing
                Market Base Rent rate and such Renewal Estimate shall be binding
                on both Landlord and Tenant as the Base Rent rate for the
                Premises during the Renewal Term. If the third appraiser
                believes that expert advice would materially assist him, he may
                retain one or more qualified persons, to provide such expert
                advice. The parties shall share equally in the costs of the
                third appraiser and of any experts retained by the third
                appraiser. Any fees of any appraiser, counsel or experts engaged
                directly by Landlord or Tenant, however, shall be borne by the
                party retaining such appraiser, counsel or expert. In the event
                that the Prevailing Market Base Rent rate has not been
                determined by the commencement date of the Renewal Term, Tenant
                shall pay Base Rent upon the terms and conditions in effect for
                initial Term until such time as the Prevailing Market Base Rent
                rate has been determined. Upon such determination, the Base Rent
                for the Premises during the Renewal Term shall be retroactively
                adjusted to the commencement of the Renewal Term. If such
                adjustment results in an underpayment of Base Rent by Tenant,
                Tenant shall pay Landlord the amount of such underpayment within
                30 days after the determination thereof. If such adjustment
                results in an overpayment of Base Rent by Tenant, Landlord shall
                credit such overpayment against the next installment of Base
                Rent due under the Lease and, to the extent necessary, any
                subsequent installments until

                                      E-3
<PAGE>   51

                the entire amount of such overpayment has been credited against
                Base Rent.

        E.      If Tenant is entitled to and properly exercises its Renewal
                Option, Landlord shall prepare an amendment (the "Renewal
                Amendment") to reflect changes in the Base Rent, Term,
                Termination Date and other appropriate terms. The Renewal
                Amendment shall be:

                1.      sent to Tenant within a reasonable time after receipt of
                        the Binding Notice; and

                2.      executed by Tenant and returned to Landlord within 15
                        days after its submission to Tenant.

                An otherwise valid exercise of the Renewal Option shall, at
                Landlord's option, be fully effective whether or not the Renewal
                Amendment is executed.

        F.      For purposes of this Renewal Option, "Prevailing Market" shall
                mean the arms length fair market annual rental rate per rentable
                square foot under renewal leases and amendments entered into on
                or about the date on which the Prevailing Market is being
                determined hereunder for space comparable to the Premises
                (without taking into consideration the value of alterations to
                the Premises made by Tenant which were in excess of the
                Allowance provided by Landlord) in the Building and office
                buildings comparable to the Building in the downtown financial
                district of San Francisco, California. The determination of
                Prevailing Market shall take into account any material economic
                differences between the terms of this Lease and any comparison
                lease, such as rent abatements, construction costs and other
                concessions and the manner, if any, in which the Landlord under
                any such lease is reimbursed for operating expenses and taxes.
                The determination of Prevailing Market shall also take into
                consideration any reasonably anticipated changes in the
                Prevailing Market rate from the time such Prevailing Market rate
                is being determined and the time such Prevailing Market rate
                will become effective under this Lease.

        G.      Landlord and Tenant acknowledge and agree that Tenant's Renewal
                Option is personal to Tenant only and not transferable to any
                other entity (except in connection with a Permitted Transfer)
                and in no event shall be exercisable by Tenant on behalf of any
                potential assignees or sublessees (except in connection with a
                Permitted Transfer).

II.     EXPANSION OPTION.

        A.      Tenant shall have the option (the "Expansion Option") to lease
                the 34,319 square feet of rentable area located on the 2nd floor
                of the Spear Tower of the Building and shown cross-hatched on
                EXHIBIT A-3 to this Lease (the "Expansion Space") if:

                1.      Landlord receives written notice (the "Expansion
                        Notice") from Tenant of the exercise of its Expansion
                        Option on or before June 30, 2004; and

                2.      Tenant is not in Monetary Default or material
                        non-monetary default under this Lease at the time
                        Landlord receives the Expansion Notice; and

                3.      no more than 16,500 rentable square feet of the Premises
                        (in the aggregate) is sublet (other than pursuant to a
                        Permitted Transfer) at the time Landlord receives the
                        Expansion Notice; and

                4.      this Lease has not been assigned (other than pursuant to
                        a Permitted Transfer) prior to the time Landlord
                        receives the Expansion Notice; and

                5.      the Expansion Space is intended for the exclusive use of
                        Tenant only during the Lease Term; and

                6.      Tenant has not vacated or abandoned the Premises at the
                        time Landlord receives the Expansion Notice.

                                      E-4
<PAGE>   52

        B.      1.      The initial annual Base Rent rate per square foot for
                        the Expansion Space shall be the Prevailing Market Rate
                        (hereinafter defined) per square foot for the Expansion
                        Space. Base Rent shall increase, if at all, in
                        accordance with the increases assumed in the
                        determination of Prevailing Market Rate. Base Rent
                        attributable to the Expansion Space, as determined in
                        Landlord's discretion, shall be payable in monthly
                        installments in accordance with the terms and conditions
                        of Article IV of the Lease.

                2.      Tenant shall pay Additional Rent for the Expansion Space
                        on the same terms and conditions set forth in Article IV
                        of this Lease, provided that Tenant's Pro Rata Share
                        shall increase appropriately to account for the addition
                        of the Expansion Space.

        C.      The term for the Expansion Space shall commence on July 1, 2005
                (the "Expansion Space Commencement Date"). Notwithstanding the
                foregoing to the contrary, the Expansion Space Commencement Date
                shall be delayed to the extent that Landlord fails to deliver
                possession of the Expansion Space for any reason, including but
                not limited to, holding over by prior occupants. Any such delay
                in the Expansion Space Commencement Date shall not subject
                Landlord to any liability for any loss or damage resulting
                therefrom. If the Expansion Space Commencement Date is delayed,
                the Termination Date under the Lease shall not be similarly
                extended. The Expansion Space shall be considered Premises,
                subject to all the terms and conditions of this Lease, except
                that no allowances, credits, abatements or other concessions (if
                any) set forth in this Lease for the initial Premises shall
                apply to the Expansion Space. Tenant hereby acknowledges that
                the Expansion Space is currently leased by Landlord to Arthur J.
                Gallagher & Co. Insurance Brokers of California, Inc., d/b/a
                Gallagher Heffernan, a California corporation pursuant to the
                terms of a lease dated October 13, 1994, as the same may be
                amended from time to time (the "Expansion Lease").
                Notwithstanding anything herein to the contrary, if the
                Expansion Lease terminates (or the existing tenant's right to
                possession is terminated) prior to its stated expiration date
                due to a default by the tenant under the Expansion Lease,
                Landlord, at its option, may provide Tenant with written notice
                of such prior termination (the "Prior Termination Notice"). If
                Landlord provides Tenant with a Prior Termination Notice, Tenant
                shall have the option to lease the Expansion Space in accordance
                with the terms and conditions set forth above, except that the
                Expansion Notice shall be due within thirty (30) days after the
                date of Landlord's Prior Termination Notice and the commencement
                date for such Expansion Space shall be the first day of the
                month following Landlord's receipt of Tenant's Expansion Notice.
                If Tenant does not provide Landlord with an Expansion Notice
                within such thirty (30) day period or if Tenant is not entitled
                to exercise its Expansion Option due to a violation of one of
                the conditions set forth in paragraph A above, Tenant's
                Expansion Option shall be deemed to be null and void and Tenant
                shall have no further rights to lease the Expansion Space
                hereunder.

        D.      The Expansion Space (including improvements and personalty, if
                any) shall be accepted by Tenant in its "as-built" condition and
                configuration existing on the earlier of the date Tenant takes
                possession of the Expansion Space or as of the date the term for
                the Expansion Space commences.

        E.      If Tenant is entitled to and properly exercises the Expansion
                Option, Landlord shall prepare an amendment (the "Expansion
                Amendment") to reflect the Expansion Space Commencement Date and
                the changes in Base Rent, Rentable Area of the Premises,
                Tenant's Pro Rata Share and other appropriate terms. A copy of
                the Expansion Amendment shall be (1) sent to Tenant within a
                reasonable time after receipt of the Expansion Notice, and (2)
                executed by Tenant and returned to Landlord in within fifteen
                (15) days thereafter.

        F.      1.      Within fifteen (15) days after receipt of Tenant's
                        Expansion Notice, Landlord shall advise Tenant of the
                        Prevailing Market Rate for the Expansion Space (the
                        "Prevailing Market Notice"). Notwithstanding the
                        foregoing, Landlord shall not be obligated to provide
                        Tenant with a Prevailing Market Notice prior to June 30,
                        2004. If Tenant, in its

                                      E-5
<PAGE>   53

                        reasonable judgment, determines that the rate set forth
                        in Landlord's Prevailing Market Notice does not
                        accurately reflect the Prevailing Market Rate for the
                        Expansion Space, Tenant shall provide Landlord with
                        written notice of rejection (the "Rejection Notice")
                        within fifteen (15) days after the date of Landlord's
                        Prevailing Market Notice. Tenant's failure to provide
                        Landlord with a Rejection Notice within such fifteen
                        (15) day period shall be deemed to be an acceptance by
                        Tenant of the Prevailing Market Rate designated by
                        Landlord. If Tenant provides Landlord with a Rejection
                        Notice in a timely manner, Landlord and Tenant shall
                        work together in good faith to determine the Prevailing
                        Market Rate for the Expansion Space. If Landlord and
                        Tenant fail to agree upon the Prevailing Market Rate
                        within thirty (30) days after the date of the Rejection
                        Notice, Tenant's exercise of the Expansion Option shall
                        be null and void and of no further force and effect.

                2.      For purposes hereof, Prevailing Market Rate shall mean
                        the annual rental rate per square foot, as determined in
                        Landlord's discretion, for space comparable to the
                        Expansion Space in the Building and office buildings
                        comparable to the Building under leases and renewal and
                        expansion amendments being entered into at or about the
                        time that Prevailing Market Rate is being determined
                        giving appropriate consideration to tenant concessions,
                        tenant improvement allowances, and the method of
                        allocating Expenses and Taxes. Notwithstanding the
                        foregoing, space leased under any of the following
                        circumstances shall not be considered to be comparable
                        for purposes hereof: (i) the lease term is for less than
                        five (5) years, (ii) the space is encumbered by the
                        option rights of another tenant, or (iii) the space has
                        a lack of windows and/or an awkward or unusual shape or
                        configuration. The foregoing is not intended to be an
                        exclusive

        G.      Notwithstanding any of the foregoing to the contrary, Tenant's
                Expansion Option set forth herein is expressly subject and
                subordinate to the renewal or extension rights of Arthur J.
                Gallagher & Co. Insurance Brokers of California, Inc. d/b/a
                Gallagher Heffernan (and any successor or assignee thereto)
                whether or not set forth in such tenant's lease, and regardless
                of whether such renewal or extension is consummated pursuant to
                a lease amendment or a new lease.

III.    AON CONTINGENCY. This Lease specifically is contingent upon the
        termination of that certain lease dated October 20, 1987, as amended
        (the "Aon Lease"), by and between Landlord (as successor in interest to
        One Market Plaza, a joint venture of the Equitable Life Assurance
        Society of the United States and Southern Pacific Land Company), and Aon
        Risk Services, Inc. of Northern California Insurance Services, a
        California corporation ("Aon") (as successor in interest to Frank B.
        Hall & Co. of California) relating to the Spear Premises, which is a
        portion of the Premises to be leased to Tenant pursuant to the terms of
        this Lease. Landlord currently is negotiating the terms of an agreement
        with Aon to terminate the Aon Lease (the "Aon Termination Agreement")
        effective on or before November 1, 2000. If Landlord fails to enter into
        the Aon Termination Agreement calling for the termination of the Aon
        Lease on or before February 1, 2001, with Aon on or before February 1,
        2001 with all contingencies thereto having been satisfied by such date,
        Landlord shall notify Tenant of that event, and Landlord may thereafter
        terminate this Lease with respect to the Spear Premises by providing
        written notice thereof to Tenant. Landlord shall use commercially
        reasonable efforts to enter in to the Aon Termination Agreement and
        satisfy all contingencies thereto. Landlord shall have no obligation to
        commence any ADA Modifications in any portion of the Premises until the
        foregoing contingency is satisfied or otherwise waived by Landlord in
        writing and Tenant has delivered executed copies of this Lease, together
        with all security deposits and prepaid rental required hereunder to
        Landlord.

IV.     DEL MONTE LEASE. Landlord and Tenant acknowledge that Landlord currently
        intends to negotiate an early termination agreement (the "Del Monte
        Termination Agreement") with respect to that certain lease dated August
        2, 1973, as amended (the "Del Monte Lease"), by and between Landlord (as
        successor in interest to One Market Plaza, a joint venture of the
        Equitable Life Assurance Society of the United States and Southern
        Pacific Land Company), and Del Monte Corporation, a New York corporation
        ("Del Monte") relating to the Steuart Premises, which is a portion of
        the Premises to be leased to Tenant pursuant

                                      E-6
<PAGE>   54

        to the terms of this Lease. Landlord and Tenant further acknowledge and
        agree that the anticipated dates for the 4th Floor Steuart Premises
        Commencement Date and the 6th Floor Steuart Premises Commencement Date
        set forth in this Lease are based upon an assumption that Landlord and
        Del Monte will successfully negotiate and execute the Del Monte
        Termination Agreement which shall provide for an early termination of
        the Del Monte Lease effective as of November 1, 2000 as to the 6th Floor
        Steuart Premises and effective as of February 1, 2001 as to the 4th
        Floor Steuart Premises. Notwithstanding any of the foregoing to the
        contrary, Landlord shall have no obligation to negotiate or execute the
        Del Monte Termination Agreement, and if Landlord and Del Monte fail to
        enter into the Del Monte Termination Agreement calling for the
        termination of the Del Monte Lease on or before November 1, 2000 as to
        the 6th floor of the Steuart Premises and on or before February 1, 2001
        as to the 4th floor of the Steuart Premises, (i) any such delay in the
        4th Floor Steuart Premises Commencement Date or the 6th Floor Steuart
        Premises Commencement Date shall not subject Landlord to any liability
        for any loss or damage resulting therefrom, (ii) the obligations of
        Landlord and Tenant under this Lease shall remain in full force and
        effect, and (iii) the 4th Floor Steuart Premises Commencement Date and
        the 6th Floor Steuart Premises Commencement Date shall be determined as
        provided in Article I.G. of this Lease

        IN WITNESS WHEREOF, Landlord and Tenant have executed this exhibit as of
the day and year first above written.

                                       LANDLORD:

                                       EOP-ONE MARKET, L.L.C., A DELAWARE
                                       LIMITED LIABILITY COMPANY

                                       By:  EOP Operating Limited Partnership,
                                            a Delaware limited partnership, its
                                            sole member

                                            By:  Equity Office Properties Trust,
                                                 a Maryland real estate
                                                 investment trust, its managing
                                                 general partner

                                                 By:    ________________________

                                                 Name:  ________________________

                                                 Title: ________________________

                                       TENANT:

                                       OMNISKY CORPORATION, A DELAWARE
                                       CORPORATION

                                       By:     _____________________________
                                       Name:   _____________________________
                                       Title:  _____________________________

                                       By:     _____________________________
                                       Name:   _____________________________
                                       Title:  _____________________________

                                      E-7
<PAGE>   55

                                    EXHIBIT F

                                PARKING AGREEMENT

        This Exhibit is attached to and made a part of the Lease dated as of the
____ day of _____________, 2000, by and between EOP-ONE MARKET, L.L.C., A
DELAWARE LIMITED LIABILITY COMPANY ("Landlord") and OMNISKY CORPORATION, A
DELAWARE CORPORATION ("Tenant") for space in the Spear Tower and the Steuart
Tower in the Building located at One Market, San Francisco, California.

1.      During the Term, Tenant agrees to lease from Landlord and Landlord
        agrees to lease to Tenant a total of 56 parking spaces (the "Spaces")
        for the use of Tenant and its employees. Of the 56 Spaces allotted to
        Tenant, 17 shall be located in the on site parking garage (based on the
        ratio of 1 parking space per 8,000 rentable square feet of the Premises)
        (the "On-site Garage") and 39 shall be located in the off site parking
        garage located at 75 Howard Street (based on the ratio of 1 parking
        space per 3,500 rentable square feet of the Premises) (the "Off-site
        Garage"). Notwithstanding the foregoing to the contrary, prior to the
        Final Commencement Date, Landlord and Tenant acknowledge and agree that
        Tenant shall only be entitled to use the Spaces as applicable to that
        portion of the Premises for which the commencement date has occurred.
        However, from and after the Final Commencement Date, Tenant shall be
        entitled to use all of the Spaces as provided herein. No deductions or
        allowances shall be made for days when Tenant or any of its employees
        does not utilize the parking facilities or for Tenant utilizing less
        than all of the Spaces. Tenant shall not have the right to lease or
        otherwise use more than the number of reserved and unreserved Spaces set
        forth above.

2.      Tenant shall pay Landlord, as Additional Rent in accordance with Article
        IV of the Lease, the then prevailing market monthly charges established
        from time to time by Landlord for parking. No deductions from the
        monthly charge shall be made for days on which the Spaces are not used
        by Tenant.

3.      Except for particular spaces and areas designated by Landlord for
        reserved parking, all parking shall be on an unreserved, first-come,
        first-served basis.

4.      Landlord shall have the right from time to time to designate the
        location of the Spaces and to promulgate reasonable rules and
        regulations regarding the On-site Garage, the Off-site Garage, the
        Spaces and the use thereof, including, but not limited to, rules and
        regulations controlling the flow of traffic to and from various parking
        areas, the angle and direction of parking and the like. Tenant shall
        comply with and cause its employees to comply with all such rules and
        regulations as well as all reasonable additions and amendments thereto.

5.      Tenant shall not store or permit its employees to store any automobiles
        in the On-site Garage or in the Off-site Garage without the prior
        written consent of Landlord. Except for emergency repairs, Tenant and
        its employees shall not perform any work on any automobiles while
        located in the On-site Garage, in the Off-site Garage, or on the
        Project. If it is necessary for Tenant or its employees to leave an
        automobile in the On-site Garage or in the Off-site Garage overnight,
        Tenant shall use reasonable efforts to provide Landlord with prior
        notice thereof designating the license plate number and model of such
        automobile.

6.      Landlord shall have the right to temporarily close the On-site Garage or
        Off-site Garage, or certain areas therein in order to perform necessary
        repairs, maintenance and improvements to the On-site Garage or the
        Off-site Garage. Landlord shall have a right to terminate this Lease as
        to the Off-site Garage Spaces on 30 days' prior notice to Tenant should
        Landlord cease to own the Off-site Garage or should Landlord or an agent
        of Landlord cease to operate the Off-site Garage, or if Landlord decides
        to remodel, remove, demolish or redevelop the Off-site Garage or any
        substantial portion thereof.

7.      Tenant shall not assign or sublease any of the Spaces without the
        consent of Landlord. Landlord shall have the right to terminate this
        Parking Agreement with respect to any Spaces that Tenant desires to
        sublet or assign.

                                       F-1
<PAGE>   56

8.      Landlord may elect to provide parking cards or keys to control access to
        the On-site Garage or Off-site Garage. In such event, Landlord shall
        provide Tenant with one card or key for each Space that Tenant is
        leasing hereunder, provided that Landlord shall have the right to
        require Tenant or its employees to place a deposit on such access cards
        or keys and to pay a fee for any lost or damaged cards or keys.

9.      NO LIABILITY. TENANT ACKNOWLEDGES AND AGREES THAT, TO THE FULLEST EXTENT
        PERMITTED BY LAW, LANDLORD SHALL NOT BE RESPONSIBLE FOR ANY LOSS OR
        DAMAGE TO TENANT OR TENANT'S PROPERTY (INCLUDING, WITHOUT LIMITATIONS,
        ANY LOSS OR DAMAGE TO TENANT'S AUTOMOBILE OR THE CONTENTS THEREOF DUE TO
        THEFT, VANDALISM OR ACCIDENT) ARISING FROM OR RELATED TO TENANT'S USE OF
        THE SPACES OR EXERCISE OF ANY RIGHTS UNDER THIS PARKING AGREEMENT. THE
        LIMITATION ON LANDLORD'S LIABILITY UNDER THE PRECEDING SENTENCE SHALL
        NOT APPLY HOWEVER TO LOSS OR DAMAGE ARISING DIRECTLY FROM LANDLORD'S OR
        ITS AGENTS' OR EMPLOYEES' NEGLIGENCE OR WILLFUL MISCONDUCT.

10.     Release of Liability. Without limiting the provisions of this Parking
        Agreement, except to the extent caused by Landlord's or its agents' or
        employees' negligence or willful misconduct, Tenant hereby voluntarily
        releases, discharges, waives and relinquishes any and all actions or
        causes of action for personal injury or property damage occurring to
        Tenant arising as a result of parking in the Spaces, or any activities
        incidental thereto, wherever or however the same may occur, and further
        agrees that Tenant will not prosecute any claim for personal injury or
        property damage against Landlord or any of its officers, agents,
        servants or employees for any said causes of action, except to the
        extent caused by Landlord's, its agents' or employees' negligence or
        willful misconduct.

11.     The provisions of Article XXI of the Lease are hereby incorporated by
        reference as if fully recited.

        Tenant acknowledges that Tenant has read the provisions of this Parking
Agreement, has been fully and completely advised of the potential dangers
incidental to parking in the Spaces and is fully aware of the legal consequences
of signing this instrument.

                                      F-2
<PAGE>   57

        Landlord and Tenant have executed this exhibit as of the day and year
first above written.

                                       LANDLORD:

                                       EOP-ONE MARKET, L.L.C., A DELAWARE
                                       LIMITED LIABILITY COMPANY

                                       By:  EOP Operating Limited Partnership,
                                            a Delaware limited partnership, its
                                            sole member

                                            By:  Equity Office Properties Trust,
                                                 a Maryland real estate
                                                 investment trust, its managing
                                                 general partner

                                                 By:    ________________________

                                                 Name:  ________________________

                                                 Title: ________________________

                                       TENANT:

                                       OMNISKY CORPORATION, A DELAWARE
                                       CORPORATION

                                       By:     _____________________________
                                       Name:   _____________________________
                                       Title:  _____________________________

                                       By:     _____________________________
                                       Name:   _____________________________
                                       Title:  _____________________________

                                      F-3
<PAGE>   58

                                    EXHIBIT G

                            FORM OF LETTER OF CREDIT

                            ------------------------
                        [Name of Financial Institution]

                                                   Irrevocable Standby
                                                   Letter of Credit
                                                   No. ______________________
                                                   Issuance Date:_____________
                                                   Expiration Date:____________
                                                   Applicant:__________________

Beneficiary

EOP-One Market, L.L.C.
One Market Street
Spear Tower
Suite 725
San Francisco, California 94105
Attention:  Leasing Director

Ladies/Gentlemen:

        We hereby establish our Irrevocable Standby Letter of Credit in your
favor for the account of the above referenced Applicant in the amount of
________________ U.S. Dollars ($__________) available for payment at sight by
your draft drawn on us when accompanied by the following documents:

1.      An original copy of this Irrevocable Standby Letter of Credit.

2.      Beneficiary's dated statement purportedly signed by one of its officers
        reading: "This draw in the amount of ______________________ U.S. Dollars
        ($____________) under your Irrevocable Standby Letter of Credit No.
        ____________________ represents funds due and owing to us as a result of
        the Applicant's default beyond applicable notice and cure periods under
        one or more of the terms of that certain lease by and between
        ______________________, as landlord, and _____________, as tenant."

        It is a condition of this Irrevocable Standby Letter of Credit that it
will be considered automatically renewed for a one year period upon the
expiration date set forth above and upon each anniversary of such date, unless
at least sixty (60) days prior to such expiration date or applicable anniversary
thereof, we notify you in writing by certified mail, return receipt requested,
that we elect not to so renew this Irrevocable Standby Letter of Credit. A copy
of any such notice shall also be sent to: Equity Office Properties Trust, 2
North Riverside Plaza, Suite 2200, Chicago, IL 60606, Attention: Senior Vice
President-Treasurer. Upon receipt of such notice, you may draw hereunder by
providing us with a dated statement proportedly signed by one of Beneficiary's
officers stating that the Applicant has failed to provide you with an acceptable
substitute irrevocable standby letter of credit in accordance with the terms of
the above referenced lease. We further acknowledge and agree that: (a) upon
receipt of the documentation required herein, we will honor your draws against
this Irrevocable Standby Letter of Credit without inquiry into the accuracy of
Beneficiary's signed statement and regardless of whether Applicant disputes the
content of such statement; and (b) this Irrevocable Standby Letter of Credit
shall permit partial draws and, in the event you elect to draw upon less than
the full stated amount hereof, the stated amount of this Irrevocable Standby
Letter of Credit shall be automatically reduced by the amount of such partial
draw. This Irrevocable Standby Letter of Credit is transferable without any
charges to the Beneficiary. In the event of transfer, the attached Annex A must
be completed and presented to us together with the original copy of this
Irrevocable Standby Letter of Credit.

        This Irrevocable Standby Letter of Credit is subject to the Uniform
Customs and Practice for Documentary Credits (1993 revision) ICC Publication No.
500.

        We hereby engage with you to honor drafts and documents drawn under and
in compliance with the terms of this Irrevocable Standby Letter of Credit.

                                       G-1
<PAGE>   59

        All communications to us with respect to this Irrevocable Standby Letter
of Credit must be addressed to our office located at
______________________________________________ to the attention of
__________________________________.

                                            Very truly yours,

                                            ------------------------------------

                                                           [name]
                                            ------------------------------------

                                                           [title}
                                            ------------------------------------

                                      G-2
<PAGE>   60

                                    EXHIBIT H

                            FORM OF WARRANT AGREEMENT

                                       H-1
<PAGE>   61

                                    EXHIBIT I

            AGREEMENT OF SUBORDINATION, NON-DISTURBER AND ATTORNMENT

        THIS AGREEMENT made the ____ day of ________, 2000, by and among EOP-ONE
MARKET, L.L.C., A DELAWARE LIMITED LIABILITY COMPANY (hereinafter called "Ground
Lessor"), OMNISKY CORPORATION, A DELAWARE CORPORATION (hereinafter called
"Tenant") and TEACHERS INSURANCE AND ANNUITY ASSOCIATION OF AMERICA, A NEW YORK
CORPORATION, having its principal office and post office address at 730 Third
Avenue, New York, New York 10017 (hereinafter called "Teachers");

                                   WITNESSETH:

        WHEREAS, Ground Lessor is the owner in fee simple of those certain
premises situate, lying and being in the City of San Francisco, County of San
Francisco, State of California, as more particularly described in Exhibit A
attached hereto; and

        WHEREAS, under the terms of a certain lease dated April 16, 1973,
(hereinafter called "Ground Lease"), a short form of which has been recorded on
April 24, 1973, Book B755 at Page 597, Series No. V71530 and an Assignment and
Assumption of Tenant's Interest in Lease recorded November 22, 1994, Book G263,
Page 204, Series No. 94-F716286-00, Official Records, San Francisco County,
State of California, amended by First Amendment to Lease Agreement recorded
October 3, 1995 in Reel G479, Image 280, Ground Lessor did lease, let and demise
the Demised Premises to EOP-ONE MARKET, L.L.C., A DELAWARE LIMITED LIABILITY
COMPANY (hereinafter called "Landlord") for a term of 99 years commencing April
16, 1973, and continuing to and including April 15, 2072, upon the terms and
conditions therein more particularly set forth;

        WHEREAS, Teachers is the owner and holder of a certain promissory note
dated September 29, 1995, secured by a Deed of Trust and Assignment of Rents and
Fixture Filing Statement of even date therewith, recorded on October 3, 1995, as
Document F866003, in the Official Records aforesaid, constituting a first lien
upon the fee simple estate in the Demised Premises as well as upon the leasehold
estate created by said Ground Lease;

        WHEREAS, under the terms of a certain lease and amendments, if any
described in that certain Lease by and between EOP-ONE MARKET, L.L.C., A
DELAWARE LIMITED LIABILITY COMPANY and Tenant dated ______________, 2000
(hereinafter called "Sublease"), Landlord did lease, let and demise, subject to
said Ground Lease, a portion of the Demised Premises as therein more
particularly described;

        WHEREAS, the parties hereto desire to establish additional rights of
quiet and peaceful possession for the benefit of Tenant under said Sublease and
further to define the terms, covenants and conditions precedent for such
additional rights.

        NOW, THEREFORE, in consideration of the respective demises and of the
sum of One Dollar ($1.00) and other good and valuable consideration, each to the
other in hand paid, it is hereby mutually covenanted and agreed as follows:

        That Ground Lessor does hereby represent, covenant and warrant:

        (a)     That said Ground Lease is in full force and effect and
                unmodified.

        (b)     That there is no existing default under the provisions of said
                Ground Lease or in the performance of any of the terms,
                covenants, conditions or warranties thereof on the part of
                either Ground Lessor or Landlord to be observed and performed
                thereunder.

        That Ground Lessor consents to and approves the within Sublease.

        That in the event of the cancellation or termination of said Ground
Lease or of the surrender thereof, whether voluntary, involuntary or by
operation of law, prior to the expiration date of said Sublease, including any
extensions and renewals of said Sublease now provided thereunder, and subject to
the observance and performance by Tenant of all of the terms, covenants and
conditions of said Sublease on the part of Tenant to be observed and performed,
Ground Lessor does hereby covenant and warrant as follows:

                                       I-1
<PAGE>   62

        (a)     The quiet and peaceful possession of Tenant under said Sublease;

        (b)     That the Sublease shall continue in full force and effect and
                Ground Lessor shall recognize the Sublease and the Tenant's
                rights thereunder and will thereby establish direct privity of
                estate and contract as between Ground Lessor and Tenant, with
                the same force and effect and with the same relative priority in
                time and right as though the Sublease were originally made
                directly from Ground Lessor in favor of Tenant, but not in
                respect of any amendment to such Sublease not previously
                approved in writing by Ground Lessor;

        (c)     To assume such of the obligations on the part of the Landlord
                under the Sublease which are deemed to run with the land for so
                long as Ground Lessor shall be the owner in fee of said Demised
                Premises;

provided, however, Ground Lessor shall not in any way or to any extent be liable
to Tenant; unless Landlord and Ground Lessor are the same entity:

                (1)     For any past act or default on the part of the original
                        or any prior landlord under said Sublease and Tenant
                        shall have no right to assert same or any damages
                        arising therefrom as an offset or defense against Ground
                        Lessor;

                (2)     For the commencement or completion of any construction
                        or any contribution toward construction or installation
                        of any improvements upon the demised premises required
                        under said Sublease, or any expansion or rehabilitation
                        of existing improvements thereon, or for restoration of
                        improvements following any casualty not required to be
                        insured under such Sublease or for the costs of any
                        restoration in excess of the proceeds recovered under
                        any insurance required to be carried under such
                        Sublease;

                (3)     For any prepayment of rent or deposit, rental security
                        or any other sums deposited with the original or any
                        prior landlord under such Sublease and not delivered to
                        Ground Lessor; or

                (4)     For any restriction on competition beyond the Demised
                        Premises.

        That in the event of the cancellation or termination of said Ground
Lease or of the surrender thereof, whether voluntary, involuntary or by
operation of law, prior to the expiration date of said Sublease, including any
extensions and renewals of said Sublease now provided thereunder, Tenant hereby
covenants and agrees to make full and complete attornment to Ground Lessor, for
the balance of the term of the Sublease, including any extensions and renewals
thereof, now provided thereunder, upon the same terms, covenants and conditions
as therein provided, so as to establish direct privity of estate and contract as
between Ground Lessor and Tenant and with the same force and effect and relative
priority in time and right as though the Sublease were originally made directly
from Ground Lessor to Tenant, and Tenant will thereafter make all rent payments
directly to Ground Lessor, and

        That Teachers and Tenant do hereby covenant and agree that said Mortgage
or Deed of Trust shall be and the same is hereby made SUBORDINATE to said
Sublease and to the recognition and attornment agreements provided for in the
third and fourth grammatical paragraphs hereof with the same force and effect as
if said Sublease had been executed, delivered and recorded and said recognition
and attornment agreements aforesaid had been effected in each case prior to the
execution, delivery and recording of said Mortgage or Deed of Trust.

        EXCEPT, HOWEVER, that this Subordination shall not affect nor be
applicable to and does hereby expressly exclude:

        (a)     The prior right and claim under and the prior lien of said
                Mortgage or Deed of Trust in, to and upon any award or other
                compensation heretofore or hereafter to be made for any taking
                by eminent domain of any part of the Demised Premises, and as to
                the right of disposition thereof in accordance with the
                provisions of said Mortgage or Deed of Trust,

                                      I-2
<PAGE>   63

        (b)     The prior right and claim under and the prior lien of said
                Mortgage or Deed of Trust, in, to and upon any proceeds payable
                under all policies of fire and rent insurance upon the Demised
                Premises and as to the right of disposition thereof in
                accordance with the terms of said Mortgage or Deed of Trust, and

        (c)     Any lien, right, power or interest, if any, which may have
                arisen or intervened in the period between the recording of said
                Mortgage or Deed of Trust and the execution of said Sublease or
                the effective date of the recognition and attornment agreements
                aforesaid, whichever is later, and any lien or judgment which
                may arise at any time under the terms of said Sublease.

        Tenant shall not subordinate the Sublease to any other mortgage or deed
of trust so long as the Mortgage or Deed of Trust now held or to be held by
Teachers remains in effect.

        Ground Lessor and Landlord agree that the Ground Lease shall not be
modified, amended, canceled, terminated or surrendered without the express prior
written consent of Teachers.

        This Subordination may not be modified except by an agreement in writing
signed by the parties hereto.

        That the terms, covenants and conditions hereof shall inure to the
benefit of and be binding upon the respective parties hereto, their respective
heirs, executors, administrators, successors and assigns.

                                      I-3
<PAGE>   64

        IN WITNESS WHEREOF, the parties hereto have caused this writing to be
signed, sealed and delivered in their respective names and behalf, and, if a
corporation, by its officers duly authorized, on the day and year first above
written.

                                       GROUND LESSOR:

                                       EOP-ONE MARKET, L.L.C., A DELAWARE
                                       LIMITED LIABILITY COMPANY

                                       By:  EOP Operating Limited Partnership,
                                            a Delaware limited partnership, its
                                            sole member

                                            By:  Equity Office Properties Trust,
                                                 a Maryland real estate
                                                 investment trust, its managing
                                                 general partner

                                                 By:    ________________________

                                                 Name:  ________________________

                                                 Title: ________________________

                                       LANDLORD:

                                       EOP-ONE MARKET, L.L.C., A DELAWARE
                                       LIMITED LIABILITY COMPANY

                                       By:  EOP Operating Limited Partnership,
                                            a Delaware limited partnership, its
                                            sole member

                                            By:  Equity Office Properties Trust,
                                                 a Maryland real estate
                                                 investment trust, its managing
                                                 general partner

                                                 By:    ________________________

                                                 Name:  ________________________

                                                 Title: ________________________

                                       TENANT:

                                       OMNISKY CORPORATION, A DELAWARE
                                       CORPORATION

                                       By:     ______________________________
                                       Name:   ______________________________
                                       Title:  ______________________________

                                       By:     ______________________________
                                       Name:   ______________________________
                                       Title:  ______________________________

                                       LENDER:

                                       TEACHERS INSURANCE AND ANNUITY
                                       ASSOCIATION OF AMERICA

                                       By:     ______________________________
                                       Name:   ______________________________
                                       Title:  ______________________________

                                       By:     ______________________________
                                       Name:   ______________________________
                                       Title:  ______________________________

                                      I-4
<PAGE>   65

                              NOTARY ACKNOWLEDGMENT
                                 (GROUND LESSOR)

State of _______________________   )

County of ______________________   )

    On _____________________ before me, ________________________________________
personally appeared ____________________________________________________________
OF EQUITY OFFICE PROPERTIES TRUST, A MARYLAND REAL ESTATE INVESTMENT TRUST, THE
MANAGING GENERAL PARTNER, OF EOP OPERATING LIMITED PARTNERSHIP, A DELAWARE
LIMITED PARTNERSHIP, THE SOLE MEMBER, OF EOP-ONE MARKET, L.L.C., A DELAWARE
LIMITED LIABILITY COMPANY
personally known to me - OR - proved to me on the
                                basis of satisfactory evidence to be the
                                person(s) whose name(s) is/are subscribed to the
                                within instrument and acknowledged to me that
                                he/she/they executed the same in his/her/their
                                authorized capacity(ies), and that by
                                his/her/their signature(s) on the instrument the
                                person(s), or the entity upon behalf of which
                                the person(s) acted, executed the instrument.

                                WITNESS my hand and official seal.

                                ________________________________________________
                                                   Notary Public

My Commission Expires:____________________________________

--------------------------------------------------------------------------------
                                OPTIONAL SECTION

CAPACITY CLAIMED BY SIGNER

    Though statute does not require the Notary to fill in the data below, doing
so may prove invaluable to persons relying on the document.

(check one)

___     INDIVIDUAL

XXX     CORPORATE OFFICER
___
        TITLE:__________________________________

____    PARTNER(S)      ____  LIMITED

                        ____  GENERAL

____    ATTORNEY-IN-FACT

____    TRUSTEE(S)

____    GUARDIAN/CONSERVATOR

____    OTHER:__________________________

    SIGNER IS REPRESENTING:
      Name of Person(s) or Entity(ies)

EQUITY OFFICE PROPERTIES TRUST, A MARYLAND REAL ESTATE INVESTMENT TRUST, THE
MANAGING GENERAL PARTNER, OF EOP OPERATING LIMITED PARTNERSHIP, A DELAWARE
LIMITED PARTNERSHIP, THE SOLE MEMBER, OF EOP-ONE MARKET, L.L.C., A DELAWARE
LIMITED LIABILITY COMPANY
("GROUND LESSOR")

--------------------------------------------------------------------------------
                                OPTIONAL SECTION

THIS CERTIFICATE MUST BE            TITLE OR TYPE OF DOCUMENT:  SUBORDINATION
ATTACHED TO THE DOCUMENT    NON-DISTURBANCE AND ATTORNMENT AGREEMENT
DESCRIBED AT RIGHT:                         NUMBER OF PAGES_____________________

                                            DATE OF DOCUMENT____________________

                                            SIGNER(S) OTHER THAN NAMED ABOVE:

                                            ("Landlord") EOP-ONE MARKET, L.L.C.,
                                            a Delaware limited liability company
                                            ("Lender") Teachers Insurance and
                                            Annuity Association of America
                                            ("Tenant")__________________________
                                            ____________________________________

Though the data requested here is not required by law, it could prevent
fraudulent reattachment of this form.

                                      I-5
<PAGE>   66

                              NOTARY ACKNOWLEDGMENT
                                   (LANDLORD)

State of _______________________   )

County of ______________________   )

    On _____________________ before me,_________________________________________
personally appeared ____________________________________________________________
OF EQUITY OFFICE PROPERTIES TRUST, A MARYLAND REAL ESTATE INVESTMENT TRUST, THE
MANAGING GENERAL PARTNER, OF EOP OPERATING LIMITED PARTNERSHIP, A DELAWARE
LIMITED PARTNERSHIP, THE SOLE MEMBER, OF EOP-ONE MARKET, L.L.C., A DELAWARE
LIMITED LIABILITY COMPANY
personally known to me - OR - proved to me on the
                                basis of satisfactory evidence to be the
                                person(s) whose name(s) is/are subscribed to the
                                within instrument and acknowledged to me that
                                he/she/they executed the same in his/her/their
                                authorized capacity(ies), and that by
                                his/her/their signature(s) on the instrument the
                                person(s), or the entity upon behalf of which
                                the person(s) acted, executed the instrument.

                                WITNESS my hand and official seal.

                                ________________________________________________
                                                   Notary Public

My Commission Expires:__________________________

--------------------------------------------------------------------------------
                                OPTIONAL SECTION

CAPACITY CLAIMED BY SIGNER

    Though statute does not require the Notary to fill in the data below, doing
so may prove invaluable to persons relying on the document.

(check one)

____    INDIVIDUAL

XXX     CORPORATE OFFICER
___
        TITLE:__________________________________

____    PARTNER(S)      ____  LIMITED

                        ____  GENERAL

____    ATTORNEY-IN-FACT

____    TRUSTEE(S)

____    GUARDIAN/CONSERVATOR

____    OTHER:____________________

    SIGNER IS REPRESENTING:
      Name of Person(s) or Entity(ies)

EQUITY OFFICE PROPERTIES TRUST, A MARYLAND REAL ESTATE INVESTMENT TRUST, THE
MANAGING GENERAL PARTNER, OF EOP OPERATING LIMITED PARTNERSHIP, A DELAWARE
LIMITED PARTNERSHIP, THE SOLE MEMBER, OF EOP-ONE MARKET, L.L.C., A DELAWARE
LIMITED LIABILITY COMPANY ("LANDLORD")

--------------------------------------------------------------------------------
                                OPTIONAL SECTION

THIS CERTIFICATE MUST BE            TITLE OR TYPE OF DOCUMENT:  SUBORDINATION
ATTACHED TO THE DOCUMENT    NON-DISTURBANCE AND ATTORNMENT AGREEMENT
DESCRIBED AT RIGHT:                         NUMBER OF PAGES_____________________

                                            DATE OF DOCUMENT____________________

                                            SIGNER(S) OTHER THAN NAMED ABOVE:

                                            ("Ground Lessor") EOP-ONE MARKET,
                                            L.L.C., a Delaware limited
                                            liability company
                                            ("Lender") Teachers Insurance and
                                            Annuity Association of America
                                            ("Tenant")__________________________
                                            ____________________________________

Though the data requested here is not required by law, it could prevent
fraudulent reattachment of this form.

                                      I-6
<PAGE>   67

                              NOTARY ACKNOWLEDGMENT
                                    (LENDER)

State of _____________________________)

County of ____________________________)

    On _____________________ before me, ________________________________________
personally appeared ___________________________________________________________,
personally known to me - OR - proved to me on the basis of
                                satisfactory evidence to be the person(s) whose
                                name(s) is/are subscribed to the within
                                instrument and acknowledged to me that
                                he/she/they executed the same in his/her/their
                                authorized capacity(ies), and that by
                                his/her/their signature(s) on the instrument the
                                person(s), or the entity upon behalf of which
                                the person(s) acted, executed the instrument.

                                WITNESS my hand and official seal.

                                ________________________________________________
                                                  Notary Public

My Commission Expires:_______________________

--------------------------------------------------------------------------------
                                OPTIONAL SECTION

CAPACITY CLAIMED BY SIGNER

    Though statute does not require the Notary to fill in the data below, doing
so may prove invaluable to persons relying on the document.

(check one)

____    INDIVIDUAL

____    CORPORATE OFFICER

        TITLE:
        ___________________________________

____    PARTNER(S)      ____  LIMITED

                        ____  GENERAL

____    ATTORNEY-IN-FACT

____    TRUSTEE(S)

____    GUARDIAN/CONSERVATOR

____    OTHER:_________________________

    SIGNER IS REPRESENTING:
      Name of Person(s) or Entity(ies)

TEACHERS INSURANCE AND ANNUITY
ASSOCIATION OF AMERICA
            ("LENDER")

--------------------------------------------------------------------------------
                                OPTIONAL SECTION

THIS CERTIFICATE MUST BE            TITLE OR TYPE OF DOCUMENT:  SUBORDINATION
ATTACHED TO THE DOCUMENT    NON-DISTURBANCE AND ATTORNMENT AGREEMENT
DESCRIBED AT RIGHT:                         NUMBER OF PAGES_____________________

                                            DATE OF DOCUMENT____________________

                                            SIGNER(S) OTHER THAN NAMED ABOVE:

                                            ("Ground Lessor") EOP-ONE MARKET,
                                            L.L.C., a Delaware limited liability
                                            company
                                            ("Landlord") EOP-ONE MARKET, L.L.C.,
                                            a Delaware limited liability company
                                            ("Tenant")__________________________
                                             ___________________________________

Though the data requested here is not required by law, it could prevent
fraudulent reattachment of this form.

                                      I-7
<PAGE>   68

                              NOTARY ACKNOWLEDGMENT
                                    (TENANT)

State of _____________________________)

County of ____________________________)

    On _____________________ before me, ________________________________________
personally appeared ___________________________________________________________,
personally known to me - OR - proved to me on the basis of
                                satisfactory evidence to be the person(s) whose
                                name(s) is/are subscribed to the within
                                instrument and acknowledged to me that
                                he/she/they executed the same in his/her/their
                                authorized capacity(ies), and that by
                                his/her/their signature(s) on the instrument the
                                person(s), or the entity upon behalf of which
                                the person(s) acted, executed the instrument.

                                WITNESS my hand and official seal.

                                ________________________________________________
                                                   Notary Public

My Commission Expires: ______________________________

--------------------------------------------------------------------------------
                                OPTIONAL SECTION

CAPACITY CLAIMED BY SIGNER

    Though statute does not require the Notary to fill in the data below, doing
so may prove invaluable to persons relying on the document.

(check one)

____    INDIVIDUAL

____    CORPORATE OFFICER

        TITLE: _____________________________

____    PARTNER(S)      ____  LIMITED

                        ____  GENERAL

____    ATTORNEY-IN-FACT

____    TRUSTEE(S)

____    GUARDIAN/CONSERVATOR

____    OTHER: ____________________

    SIGNER IS REPRESENTING:
      Name of Person(s) or Entity(ies)

__________________________________________
__________________________________________
              ("TENANT")

--------------------------------------------------------------------------------
                                OPTIONAL SECTION

THIS CERTIFICATE MUST BE            TITLE OR TYPE OF DOCUMENT:  SUBORDINATION
ATTACHED TO THE DOCUMENT    NON-DISTURBANCE AND ATTORNMENT AGREEMENT
DESCRIBED AT RIGHT:                         NUMBER OF PAGES ____________________

                                            DATE OF DOCUMENT ___________________

                                            SIGNER(S) OTHER THAN NAMED ABOVE:

                                            ("Ground Lessor") EOP-ONE MARKET,
                                            L.L.C., a Delaware limited liability
                                            company
                                            ("Landlord") EOP-ONE MARKET, L.L.C.,
                                            a Delaware limited liability company
                                            ("Lender") Teachers Insurance and
                                            Annuity Association of America

Though the data requested here is not required by law, it could prevent
fraudulent reattachment of this form.

                                      I-8
<PAGE>   69

                                    EXHIBIT A

                                LEGAL DESCRIPTION

THE LAND REFERRED TO HEREIN IS SITUATED IN THE STATE OF CALIFORNIA, COUNTY OF
SAN FRANCISCO, CITY OF SAN FRANCISCO, AND IS DESCRIBED AS FOLLOWS:

BEGINNING AT THE POINT OF INTERSECTION OF THE NORTHWESTERLY LINE OF MISSION
STREET WITH THE SOUTHWESTERLY LINE OF STEUART STREET; THENCE NORTH 44 DEGREES
51' 51" WEST ALONG SAID SOUTHWESTERLY LINE, 334.33 FEET TO A POINT IN A LINE
PARALLEL WITH AND DISTANT 334.33 FEET NORTHWESTERLY, MEASURED AT RIGHT ANGLES,
FROM SAID NORTHWESTERLY LINE OF MISSION STREET; THENCE SOUTH 45 DEGREES 08' 09"
WEST ALONG SAID PARALLEL LINE 32 FEET AND 4-1/2 INCHES; THENCE NORTH 44 DEGREES
51' 51" WEST 6 FEET AND 1-1/2 INCHES; THENCE SOUTH 45 DEGREES 08' 09" WEST 16
FEET AND 4 INCHES; THENCE NORTH 44 DEGREES 51' 51" WEST 112 FEET AND 5-1/8
INCHES; THENCE SOUTH 45 DEGREES 08' 09" WEST 177 FEET AND 7-1/2 INCHES; THENCE
SOUTH 44 DEGREES 51' 51" EAST 112 FEET AND 5-1/8 INCHES; THENCE SOUTH 45 DEGREES
08' 09" WEST 16 FEET AND 3-1/2 INCHES; THENCE SOUTH 44 DEGREES 51' 51" EAST 6
FEET AND 1-1/2 INCHES TO A POINT IN SAID PARALLEL LINE; THENCE SOUTH 45 DEGREES
09' 09" WEST ALONG SAID PARALLEL LINE 32 FEET AND 4-1/2 INCHES TO A POINT IN THE
NORTHEASTERLY LINE OF SPEAR STREET; THENCE SOUTH 44 DEGREES 51' 51" EAST ALONG
SAID NORTHEASTERLY LINE, 334.33 FEET TO A POINT IN SAID NORTHWESTERLY LINE OF
MISSION STREET; THENCE NORTH 45 DEGREES 08' 09" EAST ALONG SAID NORTHWESTERLY
LINE 274 FEET TO THE POINT OF BEGINNING.

                                      I-9

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00012-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00012-of-00352.parquet"}]]