Exhibit 10.13

EXTENSION AGREEMENT

EXTENSION AGREEMENT which shall be known as Amendment
Number Ten, and to be attached to and form a part of the lease (which together
with any amendments, modifications and extensions thereof is hereinafter called
the "Lease"), dated March 15, 1999, between Spieker Properties, L.P.,
as Landlord, and Siebel Systems, Inc., as Tenant, covering the premises known as
the Seventh Floor, the Eighth Floor, the Ninth Floor, and a portion of the
10th Floor, known as Suite 1015, and consisting of approximately
57,969 rentable square feet, at 1900 Powell Street, Emeryville, California, and
as shown on the attached Exhibits "A.1", "A.2",
"A.3", "A.4".

Landlord and Tenant hereby agree that the term of the Lease
is hereby renewed and extended for an additional term of approximately one (1)
year, to commence on the 16th day of October, 1999 and to end on the last day of
September, 2000, subject to all of the provisions of the covenants and
agreements contained in the Lease, except:



|1)	Rental:              | Base Rent for the premises shall be:                                                                                                                                                              
|----------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|10/16/99 - 9/30/00:     | $130,430.25 per month plus increases in operating expenses
per Paragraph 4.3 of the Lease over the Calendar Year 1999.                                                                            
|2)	Term and Possession: | Tenant accepts the premises in "as is"
condition.                                                                                                                                                 
|3)	Notices:             | Tenant or Landlord may send any notice as required by the
Lease via Federal Express or similar overnight courier service in lieu of
sending notice via United States certified or registered mail.

4)  Operating Expenses.  Tenant shall pay its proportionate
share of increases in Operating Expenses over the Calendar Year 1999.

5)  Tenant Improvements.  Provided Tenant is
not in default under the Lease beyond any applicable cure period at the time
Tenant request the Tenant Improvement Allowance, Landlord shall contribute a
one-time allowance equal to $1.00 per rentable square foot ($57,969.00)
("Tenant Improvement Allowance") toward the cost of Tenant
Improvements.  Said Tenant Improvement Allowance shall be utilized by December
31, 1999.  Provided Tenant is not then in default under the Lease, Landlord
shall disburse the Tenant Improvement Allowance to Tenant upon completion of
construction of the Tenant Improvements and expiration of the time for filing of
any mechanics' liens claimed or which might be filed on account of any work
ordered by Tenant or its contractor or any subcontractor, and upon receipt by
Landlord of a certificate of completion executed by the Space Planner and
Tenant's contractor, and unconditional mechanics' lien releases (which
mechanics' lien releases shall be executed by the subcontractors, labor
suppliers and materialmen in addition to Tenant's contractor), in each case in
form and substance satisfactory to Landlord, and all appropriate bills and
supporting documentation for the work ordered by Tenant or its contractor or any
subcontractor, and reasonably requested by Landlord.

6)  Expansion.  Provided Tenant is not, and has not been, in
default of any terms and conditions of this Lease beyond any applicable cure
periods, Tenant shall have the right to lease all of the rentable area on the
Eleventh (11th) floor consisting of approximately 18,456 rentable square feet
(the " Expansion Premises"), effective December 1, 1999, and as shown
outlined in green on the attached Exhibit "B".  Tenant must notify
Landlord in writing of Tenant's desire to exercise Tenant's right to lease the
Expansion Premises no later than April 15, 1999.  In the event Tenant fails to
give Landlord notice of Tenant's election to lease such additional space within
such time period, Tenant shall have no further right, title or interest in such
additional space and this right shall terminate.  If, on the other hand, Tenant
exercises its right in the manner prescribed, Tenant shall immediately deliver
to Landlord payment for the first month's rent for such additional space (in the
same manner as provided for in this Lease), and the lease for such additional
space shall be consummated without delay. Notwithstanding anything to the
contrary herein contained, Tenant's right to the Expansion Premises shall be
conditioned upon the following:  (i) at the time Tenant agrees to accept the
Expansion Premises and at the time of the commencement of the term for the
Expansion Premises, Tenant and/or Tenant's affiliate(s) shall be in possession
of and occupying the primary premises for the conduct of its business therein
and the same shall not be occupied by any assignee, subtenant or licensee and,
provided further, that the option for additional space shall be applicable
hereunder only if the Expansion Premises will actually be occupied by Tenant and
or Tenant's affiliate(s) and (ii) the agreement of acceptance shall constitute a
representation by Tenant to Landlord, effective as of the date of the agreement
of acceptance and as of the date of commencement of the lease for the Expansion
Premises, that Tenant does not intend to assign the lease for the expansion
premises, in whole or in part or sublet all or any portion of the Premises, the
election to expand being for the purpose of utilizing the Expansion Premises for
Tenant's purposes in the conduct of Tenant's business therein.

The commencement date of the Term with respect to the  Expansion Premises
shall be referred to as the "Expansion Premises Commencement Date".
The Term with respect to the Expansion Premises shall end concurrently with the
expiration of the term of this Lease as to the original Premises.



The Basic Rent payable for the Expansion Premises shall be at the same rental
rate per square foot as the Rent for the original Premises as outlined in
Paragraph 1 of this Extension Agreement ($41,526.00 per month).

The Expansion Premises shall be leased to Tenant "as is" and in its
then existing condition and state of improvement and Landlord shall have no
obligation to make any improvements, repairs or alterations thereof; provided,
however, (i) such space shall be delivered to Tenant broom clean and in a usable
condition and (ii) Landlord shall pay to Tenant  an allowance of $.83  per
rentable square foot ($15,393.00) in the Expansion Premises.   The allowance set
forth above shall be expended for the design and installation of work which
constitutes permanent improvements to the Expansion Premises (including
carpeting) which becomes Landlord's property upon installation pursuant to this
Lease, and shall not be used for furniture, furnishings or other installations
which do not become Landlord's property pursuant to this Lease.  Tenant shall
not be entitled to any payment or rent reduction for any part of said allowance
not used by Tenant.  Said allowance shall be utilized by Tenant no later than
December 31, 1999.

Provided Tenant is not then in default under the Lease beyond
any applicable cure period, Landlord shall disburse the Tenant Improvement
Allowance to Tenant upon completion of construction of the Tenant Improvements
and expiration of the time for filing of any mechanics' liens claimed or which
might be filed on account of any work ordered by Tenant or its contractor or any
subcontractor, and upon receipt by Landlord of a certificate of completion
executed by the Space Planner and Tenant's contractor, and unconditional
mechanics' lien releases (which mechanics' lien releases shall be executed by
the subcontractors, labor suppliers and materialmen in addition to Tenant's
contractor), in each case in form and substance satisfactory to Landlord, and
all appropriate bills and supporting documentation for the work ordered by
Tenant or its contractor or any subcontractor, and reasonably requested by
Landlord.

Landlord shall have no liability to Tenant for any damages resulting from any
delay in delivering possession of the Expansion Premises to Tenant, if said
delay is caused by the holding over of a previous tenant of the Expansion
Premises; provided, however, Landlord, at its expense, shall take all action
reasonably necessary, including required legal proceedings, to secure possession
of the Expansion Premises prior to the Expansion Premises Commencement Date
therefor.

Upon the Expansion Premises Commencement Date, the term "Premises"
shall include the Expansion Premises.

7)  Option to Renew.  Tenant shall, provided
this Lease is in full force and effect and Tenant is not and has not been in
default under any of the terms and conditions of this Lease beyond any
applicable cure period, have one (1) option to renew this Lease for a term of
eighteen (18) months, for the Premises in "as is" condition and on the
same terms and conditions set forth in this Lease, except as modified by the
terms, covenants and conditions set forth below:

(1)	If Tenant elects to exercise such option, then Tenant
shall provide Landlord with written notice no earlier than January 1, 2000, and
no later than 5:00 p.m. (Pacific Standard Time) on April 1, 2000.  If Tenant
fails to provide such notice, Tenant shall have no further or additional right
to extend or renew the term of this Lease.

(2)	The Base Rent in effect at the expiration of the then
current term of this Lease shall be increased to reflect the current fair market
rental for comparable space in the Building or Project and in other similar
buildings in the same rental market as of the date the renewal term is to
commence, taking into account the specific provisions of this Lease which will
remain constant, and the Building amenities, location, identity, quality, age,
condition, term of lease, tenant improvements, services provided, and other
pertinent items.

(3)	Landlord shall advise Tenant of the new Base Rent for
the Premises for the applicable renewal term based on Landlord's determination
of fair market rental value, as well as the terms and conditions for the renewal
term, no later than fifteen (15) days after receipt of notice of Tenant's
exercise of its option to renew.

(4)	Landlord and Tenant shall negotiate in good faith to
agree on the fair market rental value of the Premises and terms and conditions
for each renewal term.  If Tenant and Landlord are unable to agree on a mutually
acceptable rental rate for any renewal term within thirty (30) days after
notification by Landlord to Tenant of Landlord's determination of the new Base
Rent for the applicable renewal term, but in any event no later than the date
which is one hundred twenty (120) days prior to the expiration of the then
current term, then on or before such date Landlord and Tenant shall each appoint
a licensed real estate broker with at least ten (10) year's experience in
leasing office space in the area in which the Building is located to act as
arbitrators.  The two (2) arbitrators so appointed shall determine the fair
market rental value for the Premises for the applicable renewal term based on
the above criteria and each shall submit his or her determination of such fair
market rental value to Landlord and Tenant in writing, within ten (10) days
after their appointment.

If the two (2) arbitrators so appointed cannot agree on the
fair market rental value for the applicable renewal term within such 10-day
period, the two (2) arbitrators shall within five (5) days thereafter appoint a
third arbitrator who shall be a licensed real estate broker with at least ten
(10) year's experience in leasing office space in the area in which the Building
is located.  The third arbitrator so appointed shall independently determine the
fair market rental value for the Premises for the renewal term within ten (10)
days after appointment, by selecting from the proposals submitted by each of the
first two arbitrators the one that most closely approximates the third
arbitrator's determination of such fair market rental value.  The third
arbitrator shall have no right to adopt a compromise or middle ground or any
modification of either of the proposals submitted by the first two arbitrators.
The proposal chosen by the third arbitrator as most closely approximating the
third arbitrator's determination of the fair market rental value shall
constitute the decision and award of the arbitrators and shall be final and
binding on the parties.

Each party shall pay the fees and expenses of the arbitrator
appointed by such party and one-half (1/2) of the fees and expenses of the third
arbitrator.

If either party fails to appoint an arbitrator, or if either
of the first two arbitrators fails to submit his or her proposal of fair market
rental value to the other party, in each case within the time periods set forth
above, then the decision of the other party's arbitrator shall be considered
final and binding.

In the event the third arbitrator fails to present a fair
market rental value within such 10-day period, then by mutual consent of the
Landlord and Tenant, the time period will be extended.

(5)	Notwithstanding anything to the contrary contained in
this Paragraph, in no event shall the Base Rent for any renewal term be less
than the Base Rent in effect at the expiration of the previous term plus expense
escalations over the previous years  In addition, Landlord shall have no
obligation to provide or pay for any tenant improvements or brokerage
commissions during any renewal term.

(6)	Tenant's right to exercise any option(s) to renew
under this Paragraph shall be conditioned upon Tenant occupying the entire
Premises and the same not being occupied by any assignee, subtenant or licensee
other than Tenant or its affiliate at the time of exercise of any option and
commencement of the renewal term.  Tenant's exercise of the option to renew
shall constitute a representation by Tenant to Landlord that as of the date of
exercise of the option and the commencement of the renewal term, Tenant does not
intend to seek to assign this Lease in whole or in part, or sublet all or any
portion of the Premises.

(7)	Any exercise by Tenant of any option to renew under
this Paragraph shall be irrevocable.  If requested by Landlord, Tenant agrees to
execute a lease amendment or, at Landlord's option, a new lease agreement on
Landlord's then standard lease form for the Building, reflecting the foregoing
terms and conditions, prior to the commencement of the renewal term.  The
option(s) to renew granted under this Paragraph is/are not transferable; the
parties hereto acknowledge and agree that they intend that each option to renew
this Lease under this Paragraph shall be "personal" to the specific
Tenant named in this Lease and that in no event will any assignee or sublessee
have any rights to exercise such option(s) to renew.

8)  Signage.  Upon execution of a lease for premises in 2100
Powell Street in which the square footage is in excess of 200,000 rentable
square feet, Tenant shall be immediately entitled to one sign to be located
above the 12th Floor on the south side of the exterior of the Building known as
1900 Powell Street.  Such sign will be designed and constructed at Tenant's sole
cost and expense.  Tenant shall pay all installation costs.  All signs shall be
subject to Landlord's approval, which shall not be unreasonably withheld or
delayed, and approval of any public authorities having jurisdiction.  Tenant
shall be responsible for electrical energy used in connection with its signs,
repairs and maintenance necessary to maintain the signs in their original
condition.  All of Tenant's signs shall at all times remain the property of
Tenant and Tenant must remove its signs at the expiration or earlier termination
of this Lease.  Tenant shall repair any damage caused in the removal of its
sign.  The parties agree that said sign will be relocated by Tenant to 2100
Powell Street upon Tenant's occupancy of 2100 Powell Street.



IN WITNESS WHEREOF, the parties hereto have executed this
Extension Agreement as of this __________ day of ____________, 199__.

LANDLORD:
SPIEKER PROPERTIES, L.P.
By:  Spieker Properties, Inc.

By:	
Its:

TENANT:

SIEBEL SYSTEMS, INC.

By:

Its: