Exhibit 10.5.1

SECOND AMENDMENT OF LEASE

This Second Amendment of Lease is made and entered into this
19th day of March, 1997, by and between Crossroads Associates and Clocktower
Associates (Landlord), and Siebel Systems, Inc. a California Corporation
(Tenant).

RECITALS

A. WHEREAS, Landlord and Tenant entered into a Lease dated June
4th, 1996, (the Lease) for the lease of approximately 66,426 gross square feet
of space located in the five story Building located at 1855 South Grant Street,
San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenant's option to lease the fourth floor of 1875 South Grant Street, and by
letter dated December 17th, 1996, Tenant exercised Tenant's option to lease the
tenth floor of the 1875 South Grant Street Building; and

C. WHEREAS, by First Amendment of Lease dated March 17, 1997
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of 1875 South
Grant Street, commencing April 1st, 1997, contingent upon Landlord obtaining a
lease termination agreement with California Federal Bank, which lease
termination agreement was not obtained thereby rendering the First Amendment of
Lease void;

D. WHEREAS, Tenant desires to lease an additional 12,926 gross
square feet of space (which includes Tenant's proportionate share of Building
common areas) located on the first floor of the Building located at 1875 South
Grant Street, San Mateo, San Mateo County, California, thereby bringing Tenant's
total leased area to 114,756 rentable square feet (66,426 s.f. + 35,404 s.f. +
12,926 s.f.).

NOW, THEREFORE, in consideration of the foregoing and other
good and valuable consideration, receipt of which is hereby acknowledged,
Landlord and Tenant agree as follows:

1. The Premises to be leased hereunder shall hereinafter be
referred to as the First Floor 1875 Space" and is described as follows: 12,926
rentable square feet of space, which includes Tenant's prorata share of Building
common areas, located on the first floor of the Building located at 1875 South
Grant Street, San Mateo, San Mateo County, California and as further outlined in
red on Exhibit "A".

2. Effective Date and Termination Date

The "Effective Date" shall hereinafter be defined as April 1st,
1998. The Lease Termination Date for the First Floor 1875 Space shall be
co-terminus with the space leased by Tenant at 1855 South Grant Street and
therefore shall be August 7th, 2006. Landlord and Tenant further agree Tenant's
Lease of the First Floor 1875 Space shall be subject to the options to extend
the Lease per paragraph 48 of the Lease.

3. Upon the Effective Date, Landlord agrees to lease to Tenant
and Tenant agrees to lease and hire from Landlord the First Floor 1875 Space as
defined above.

4. Tenant agrees to lease the First Floor 1875 Space in an
as-is condition, and any alteration or modifications to the Premises shall be
made in accordance with paragraphs 8 & 9 of the Lease and shall not delay
the commencement of Lease for the First Floor 1875 Space nor delay the payment
of rent and all such modifications shall be at Tenant's sole cost and expense.
Notwithstanding anything herein to the contrary, Landlord agrees to provide
Tenant an allowance equal to the cost to recarpet the First Floor 1875 Space
with building standard carpet and building standard base and to repaint the
First Floor 1875 Space. The allowance to be provided herein shall be in the form
of a credit against Basic Rent due and owing from Tenant to Landlord, and said
allowance shall be credited to Tenant in the month succeeding the installation
of new carpet, base, and paint for the applicable areas.

5. Basic Rent

Commencing on the Effective Date, Tenant's monthly Basic Rent
for the First Floor 1875 Space shall be l2,926s.f. x $2.30 = $29,729.80 per
month. This amount shall be adjusted on August 7th, 1998 and annually thereafter
per the terms and limitations described in paragraph 38 of the Lease. For
example, if effective August 7th, 1998 the annual rent adjustment described in
paragraph 38 of the Lease is 2.4% then Effective August 7th, 1998 Tenant's Basic
Rent for the First Floor 1875 Space will be adjusted as follows: $29,729.80 x
1.04 = $30,918.99. This amount will be adjusted annually thereafter according to
paragraph 38.

6. Additional Rent

Upon the Effective Date, Tenant's Additional Rent as described
in paragraph 4D of the Lease shall be increased by the then current rate being
charged to tenants occupying Building 1875 and shall continue to be adjusted per
the terms and conditions of paragraph 4D. For example if the Additional Rent per
square foot per month for space in the 1875 Building as of the Effective Date
was $0.62/square foot/month, commencing upon the Effective Date, Tenant's
Additional Rent would be increased by the following amount: 12,926 s.f. x $0.62
per square foot per month = $8,014 per month.

7. Parking

Upon the Effective Date, Tenant's allocated number of parking
spaces in the Complex shall be increased by 40 spaces.

8. Landlord and Tenant mutually acknowledge and agree that
neither Landlord nor Tenant have had any dealings with any real estate brokers
or agents in connection with the negotiation of this First Amendment of Lease
which has resulted in any obligation to pay a leasing
commission.

Except as herein modified the Lease shall remain in full force and
effect.

IN WITNESS WHEREOF, the parties have signed this First Amendment of Lease,
which for reference purposes shall be deemed to have been dated as the day above
written.

|LANDLORD:                                        | TENANT:                                                      
|------------------------------------------------ | -------------------------------------------------------------
|CROSSROADS ASSOCIATES, and
CLOCKTOWER ASSOCIATES | SIEBEL SYSTEMS, Inc., a
        California Corporation       
|/s/ Boyd Smith
	Title Partner                    | /s/ Howard H. Graham
      TitleSenior Vice President and CFO

---

THIRD AMENDMENT OF LEASE

This Third Amendment of Lease is made and entered into this
1st day of September, 1997, by and between Crossroads Associates and
Clocktower Associates (Landlord), and Siebel Systems, Inc. a California
Corporation (Tenant).

RECITALS

A. WHEREAS, Landlord and Tenant entered into a Lease dated June
4th, 1996, (the Lease) for the lease of approximately 66,426 gross square feet
of space located in the five story Building located at 1855 South Grant Street,
San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenant's option to lease the fourth floor of 1875 South Grant Street, and by
letter dated December 17th, 1996, Tenant exercised Tenant's option to lease the
tenth floor of the 1875 South Grant Street Building; and.

C. WHEREAS, by First Amendment of Lease dated March 17, 1997
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of 1875 South
Grant Street, commencing April 1st, 1997, contingent upon Landlord obtaining a
lease termination agreement with California Federal Bank, which lease
termination agreement was not obtained thereby rendering the First Amendment of
Lease void;

D. WHEREAS, by Second Amendment of Lease dated March 19, 1997
Tenant leased an additional 12,926 gross square feet of space (which includes
Tenant's proportionate share of Building common areas) located on the first
floor of the Building located at 1875 South Grant Street, San Mateo, San Mateo
County, California (the "First Floor 1875 Space"); and

E. WHEREAS, by letter dated May 23, 1997, Tenant exercised
Tenant's Option to lease the ninth floor of 1875 South Grant Street, and by
letter dated July 28th, 1997 Tenant exercised Tenant's Option to lease the
Eighth floor of 1875 South Grant Street, thereby bringing Tenant's total leased
area (subject to the Ninth floor becoming available) 150,160 gross square feet
of space.

F. WHEREAS, Tenant wishes to lease directly from Landlord Suite
130, 1875 South Grant Street, which Suite 130 is included in and is a part of
the First Floor 1875 space as referred to above and as is defined in paragraph 1
of the Second Amendment of Lease. Tenant's direct lease of Suite 130 is to
commence prior to the commencement of lease date for the First Floor 1875 space
of April 1st, 1998 as is currently provided for. In order to allow Tenant to do
so, California Federal Bank, has agreed to modify its May 18, 1990 lease with
Landlord (the "Cal Fed Lease") to eliminate Suite 130 from the Cal Fed Lease
premises. In addition, California Federal Bank and InCOMMON, LLC have agreed to
modify the February 21, 1997 Sublease between CalFed and inCommon (the inCommon
Sublease") to eliminate Suite 130 from the inCommon subleased premises.

NOW, THEREFORE, in consideration of the foregoing and other
good and valuable consideration, receipt of which is hereby acknowledged,
Landlord and Tenant agree as follows;

1. Suite 130. The Premises tube leased hereunder shall
hereinafter be referred to as "Suite 130" and is described as follows: 4,114
rentable square feet of space, which includes Tenant's prorata share of Building
common areas, located on the First Floor of the Building located at 1875 South
Grant Street, San Mateo, San Mateo County, California and as further outlined in
red on Exhibit "A." Suite 130 is a part of the First Floor 1875 Space as
referred to above.

2. Effective Date and Termination Date. The "Effective
Date" shall hereinafter be defined as September 1, 1997. The Lease Termination
Date for Suite 130 shall be co-terminus with the space leased by Tenant at 1855
South Grant Street and therefore shall be August 7, 2006. Landlord and Tenant
further agree Tenant's lease of Suite 130 shall be subject to the options to
extend the Lease per paragraph 48 of the Lease.

3. Agreement to Lease. Upon the Effective Date, Landlord
agrees to lease Tenant and Tenant agrees to lease and hire from Landlord Suite
130 as defined above.

4. Premises As-Is. Tenant agrees to lease Suite 130 in
an "as-is" condition, and any alteration or modifications to the Premises shall
be made in accordance with paragraphs 8 & 9 of the Lease and shall not delay
the commencement of Lease for Suite 130 nor delay the payment of rent and all
such modifications shall be at Tenant's sole cost and expense.

5. Basic Rent. Commencing on the Effective Date,
Tenant's monthly Basic Rent for Suite 130 shall be 4,114 s.f. x $1.35 =
$5,553.90 per month. This amount shall be adjusted on April 1st, 1998, which is
the Effective Date for the First Floor 1875 Space. From and after April 1st,
1998, the Basic Rent for Suite 130 shall be as described in paragraph 5 of the
Second Amendment of Lease.

6. Additional Rent

Upon the Effective Date, Tenant's Additional Rent for Suite 130
shall be $2,550.68 per month. This amount shall be increased on April 1st, 1998
to the then current rate being charged to tenants occupying Building 1875 and
shall continue to be adjusted per the terms and conditions of paragraph 4D of
the Lease.

7. Parking

Upon the Effective Date, Tenant's allocated number of parking
spaces in the Complex shall be increased by 13 spaces.

8. No Brokers. Landlord and Tenant mutually acknowledge
and agree that neither Landlord nor Tenant have had any dealings with any real
estate brokers or agents in connection with the negotiation of this Third
Amendment of Lease which has resulted in any obligation to pay a leasing
commission.

9. Lease in Full Force and Effect.Except as
herein modified the Lease shall remain in full force and effect.

IN WITNESS WHEREOF, the parties have signed this Third
Amendment of Lease, which for reference purposes shall be deemed to have been
dated as the day above written.

|LANDLORD:                                        | TENANT:                                                      
|------------------------------------------------ | -------------------------------------------------------------
|CROSSROADS ASSOCIATES, and
CLOCKTOWER ASSOCIATES | SIEBEL SYSTEMS, Inc., a
        California Corporation       
|/s/ Boyd Smith
	Title    ___________             | /s/ Howard H. Graham
      TitleSenior Vice President and CFO

---

FOURTH AMENDMENT OF LEASE

This Fourth Amendment of Lease is made and entered into this
2nd day of April, 1998, by and between Crossroads Associates and Clocktower
Associates (Landlord), and Siebel Systems, Inc. a California Corporation
(Tenant).

RECITALS

A. WHEREAS, Landlord and Tenant entered into a Lease dated June
4th, 1996, (the Lease) for the lease of approximately 66,426 gross square feet
of space located in the five story Building located at 1855 South Grant Street,
San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenant's option to lease the fourth floor of 1875 South Grant Street, and by
letter dated December 17th, 1996, Tenant exercised Tenant's option to lease the
tenth floor of the 1875 South Grant Street Building; and

C. WHEREAS, by First Amendment of Lease dated March 17, 1997
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of 1875 South
Grant Street, commencing April 1st, 1997, contingent upon Landlord obtaining a
lease termination agreement with California Federal Bank, which lease
termination agreement was not obtained thereby rendering the First Amendment of
Lease void; and

D. WHEREAS, by Second Amendment of Lease dated March 19, 1997
Tenant leased an additional 12,926 gross square feet of space (which includes
Tenant's proportionate share of Building common areas) located on the first
floor of the Building located at 1875 South Grant Street, San Mateo, San Mateo
County, California (the First Floor 1875 Space); and

E. WHEREAS, by letter dated May 23, 1997, Tenant exercised
Tenant's Option to lease the ninth floor of 1875 South Grant Street, and by
letter dated July 28th, 1997 Tenant exercised Tenant's Option to lease the
Eighth floor of 1875 South Grant Street, thereby bringing Tenant's total leased
area (subject to the Ninth floor becoming available) to 150,160 gross square
feet of space.

F. WHEREAS, by Third Amendment of Lease dated September 1st,
1997 Landlord and Tenant agreed to an early commencement of lease for Suite 130,
1875 South Grant Street, such that the Suite 130 Lease commenced September 1st,
1997.

G. WHEREAS, Tenant desires to make certain modifications to
Tenant's Leased Premises in the Building at 1875 South Grant Street, San Mateo,
which Tenant improvements will result in an increased need for parking over and
above the amount of parking spaces allocated to Tenant under the Lease and
Landlord has agreed to allocate to Tenant additional parking.

NOW, THEREFORE, in consideration of the foregoing and other
good and valuable consideration, receipt of which is hereby acknowledged,
Landlord and Tenant agree as follows:

1. The total number of parking spaces allocated to Tenant under
the Lease is summarized as follows:



|                                                                             
|-----------------------------------------------------------------------------
|Location ofPremises                                                          
|                                                                             
|18551875   1st Floor   4th
      Floor   8th Floor   10th
      Floor   Total

In addition to the number of parking spaces granted to Tenant
for the Leased Premises as summarized above, Landlord hereby agrees to provide
and grant Tenant an additional 45 parking spaces throughout the term of Tenant's
Lease or any extension thereof thereby bringing Tenant's total parking
allocation to 396 +45 = 441. If during Tenant's tenancy Landlord, in
Landlord's sole opinion, deems it necessary to specifically designate an area in
which the additional 45 spaces referred to herein shall be located, Landlord
reserves the right to so designate a specific area and Tenant agrees to use
Tenant's best efforts to encourage Tenant's employees to so park in the
designated area. The designated area may be within the parking area of the
Complex, or may be upon an adjacent parcel or parcels immediately to the north
of the Complex.

2. Compensation. As compensation to Landlord for the
additional parking allocation of 45 spaces Tenant agrees to pay Landlord, in
addition to all other Basic and Additional Rent due under the lease, the
following amounts:

Commencing upon the completion of Tenant's improvements for the
10th floor (1875) Premises, Tenant shall pay landlord $6,250.00 per month, with
partial months prorated. Upon completion of Tenant's improvements for the 8th
floor (1875) Premises, the $6,25000 monthly amount shall be increased to
$12,500.00 per month. This shall be paid and adjusted as indicated in the table
below:



|Time Period                                                                        | Monthly Amount                         
|---------------------------------------------------------------------------------- | ---------------------------------------
|(per above) - 12/31/2002                                                           | $ 12,500.00                            
|1/1/2003 - 08/07/2006(1)8/8/2006 -
      08/07/2011(2)8/8/2011 -
    08/07/2016(3) | $ 13,000.00$ 13,500.00$
      14,000.00



__________

(1)(end of original lease term)(2)(provided that
the Lease is extended per Tenant's first option).(3)(provided
Tenant exercises its second option to extend).

3. Restoration. Tenant has submitted to Landlord a
tentative schematic plan which reflects Tenant's intentions to reconfigure the
eighth and tenth floors in the Building at 1875 South Grant Street. This
preliminary plan is dated November 7, 1997 and is attached as Exhibit "A" to
this Fourth Amendment of Lease. Landlord hereby approves Tenant's preliminary
plans subject to Landlord's final review of the actual p1ans, finish schedules,
and specifications which are to plans subject to Landlord's final review of the actual p1ans, finish schedules, and specifications which are to be submitted from Tenant to Landlord per paragraph 8 & 9 of the Lease. Pursuant to Paragraphs 8 & 9 of the Lease, should Tenant make the modifications as indicated, Tenant's restoration requirements for each of the floors so modified will be as follows:

a) Construct seven private offices at each "side" of each
floor.
b) Reinstall the entire 1oop corridor on each floor.
c) Add two 15 x 15 rooms on each side of each floor.
d) Make all necessary mechanical, electrical, fire sprinkler
and other modifications necessary to achieve the above including compliance with
any building code requirements then in effect at the time such restoration is to
be performed.
e) With respect to finishes and other building standard
materials, Tenant will restore all materials and finishes to the building
standard unless unless otherwise approved and accepted in writing by
Landlord.

A preliminary drawing of the configuration of the Premises
after the restoration is performed is attached as Exhibit "B" to
this Fourth Amendment of Lease. All restoration required hereunder shall be at
Tenant's sole cost and expense and shall be performed in accordance with
paragraphs 8 and 9 of the Lease.

4. Lease in full force and effect. Except as herein
modified the Lease shall remain in full force and effect.

IN WITNESS WHEREOF, the parties have signed this Fourth
Amendment of Lease, which for reference purposes shall be deemed to have been
dated as the day above written.

|LANDLORD:                                        | TENANT:                                                      
|------------------------------------------------ | -------------------------------------------------------------
|CROSSROADS ASSOCIATES, and
CLOCKTOWER ASSOCIATES | SIEBEL SYSTEMS, Inc., a
        California Corporation       
|/s/ Boyd Smith
	Title Partner                    | /s/ Kevin A. Johnson
      TitleVice President, Legal Affairs

---

FIFTH AMENDMENT TO LEASE

This Fifth Amendment of Lease is made and entered into this 8th
day of May, 1998, by and between Crossroads Associates and Clocktower Associates
(Landlord), and Siebel Systems, Inc. a California Corporation (Tenant).

RECITALS

A. WHEREAS, Landlord and Tenant entered into a Lease dated June
4th, 1996, (the Lease) for the lease of approximately 66,426 gross square feet
of space located in the five story Building located at 1855 South Grant Street,
San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenant's option to lease the fourth floor of the Building located at 1875 South
Grant Street, San Mateo, San Mateo County, California (and hereinafter referred
to as the 1875 Building) and by letter dated December 17th, 1996, Tenant
exercised Tenant's option to lease the tenth floor of the 1875 Building; and

C. WHEREAS, by First Amendment of Lease dated March 17, 1997
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of the 1875
Building, commencing April 1st, 1997, contingent upon Landlord obtaining a lease
termination agreement with California Federal Bank, which lease termination
agreement was not obtained thereby rendering the First Amendment of Lease void;
and

D. WHEREAS, by Second Amendment of Lease dated March 19, 1997
Tenant leased an additional 12,926 gross square feet of space located on the
first floor of the 1875 Building; and

E. WHEREAS, by letter dated May 23, 1997, Tenant exercised
Tenant's Option to lease the ninth floor of the 1875 Building, and by letter
dated July 28th, 1997 Tenant exercised Tenant's Option to lease the Eighth floor
of the 1875 Building, thereby bringing Tenant's total leased area (subject to
the Ninth floor becoming available) to 150,160 gross square feet of space;
and

F. WHEREAS, by Third Amendment of Lease dated September 1st,
1997 Landlord and Tenant agreed to an early commencement of lease for Suite 130,
in the 1875 Building, such that the Suite 130 Lease commenced September 1st,
1997.

G. WHEREAS, by Fourth Amendment of Lease dated April 2nd, 1998,
Landlord and Tenant agreed that Landlord will allow Tenant to make certain
improvements to Tenant's Premises in the 1875 Building and Tenant further agreed
to additional compensation for additional parking.

H. WHEREAS, Bay Networks exercised its option to extend its
lease on the ninth floor of the 1875 Building, thereby making Tenant's exercise
of option to lease the ninth floor void and therefore bringing Tenant's total
leased area to 132,458 square feet.

I. WHEREAS, in the 1875 Building Tenant now desires to lease an
additional 9,453 square feet on the second floor and 6,973 square feet on the
third floor (which include Tenant's proportionate share of building common
areas), thereby bringing Tenant's total leased area to 148,884 square feet.

NOW, THEREFORE, in consideration of the foregoing and other
good and valuable consideration, receipt of which is hereby acknowledged,
Landlord and Tenant agree as follows:

1. The areas to be leased hereunder are all located in the
Building located at 1875 South Grant Street, San Mateo, San Mateo County,
California and are further described as follows:

a) Suite 200

Comprising 8,007 square feet of rentable space, including
Tenant's prorata share of Building common areas, located on the second floor and
as further described in red on Exhibit "Al".

b) Suite 220

Comprising 1,376 gross square feet of space, which includes
Tenant's prorata share of Building common areas, located on the second floor and
as further outlined in red on Exhibit "Al".

c) Suite 350

Comprising 6,973 rentable square feet of space, which includes
Tenant's prorata share of Building common areas, located on the third floor and
as further outlined in red on Exhibit "A2".

Tenant hereby acknowledges that all three suites to be leased
hereunder, Suite 200, 220 and 350, are currently leased to other tenants.
Tenant's Lease of Suite 200 and Suite 350 are each contingent upon Landlord
entering into, in Landlord's sole opinion, an acceptable Lease Termination
Agreement, specifying the date upon which such leases shall terminate (each a
"Lease Termination Date"), with each of the respective tenants that lease and
occupy Suites 200 & 350. In the event Landlord does not enter into such a
lease termination agreement with respect to the tenants leasing suite 200 or
350, then the provisions of this Fifth Amendment of Lease applicable to the
suite for which Landlord does not enter such lease termination agreement shall
be void and of no force and effect between the parties and neither Landlord nor
Tenant shall be liable to one another for having entered into this Fifth
Amendment of Lease with respect to such space. All other terms and conditions of
the Lease, including the other terms and conditions of this Fifth Amendment of
Lease, shall remain in full force and effect.

2. EFFECTIVE DATE

The "Effective Date" for the commencement of Lease for Suites
200 and 350 shall be the calendar date immediately succeeding the Lease
Termination Date for Suite 200 and 350 respectively. The Effective Date for
Suite 220 shall be the later of September 1st, 1998 or the date Landlord
delivers possession of Suite 220 to Tenant. It is anticipated by Landlord and
Tenant that the Effective Date for Suite 200 shall be June 16, 1998 and for
Suite 350 August 1st, 1998.

3. TERM

The Term of Lease for Suite 200, 220, and 350, shall each
commence upon the Effective Date for each of the respective Suites and shall
terminate August 31st, 2008. Landlord and Tenant each acknowledge that the
expiration date of the term of Lease for Suites 200, 220, and 350 leased
hereunder is different from the expiration date of the term of lease for the
1855 Building and Tenant's lease for the 1st, 4th, 8th and 10th floor spaces in
the 1875 Building, (hereinafter referred to for purposes of this Fifth Amendment
of Lease as the "Core Space"). In the event the term of Tenant's lease for the
Core Space expires and Tenant vacates the Core Space, nevertheless, the term of
lease for Suites 200, 220 and 350 leased hereunder shall expire August 31st,
2008 and all the terms and conditions of the Lease shall remain in full force
and effect and shall pertain to the space leased under this Fifth Amendment of
Lease. Furthermore, it is hereby agreed that the Lease for Suite 200, 220 and
350 shall be subject to the Option to Extend granted to Tenant per paragraph 48
of the Lease. In the event that Tenant exercises its option to extend the Lease
on the Core Space (as defined above) such that the Lease for the Core Space is
extended to July 31st, 2011, then the Lease for Suites 200, 220 and 350 shall
automatically be extended from August 31st, 2008 to July 31st, 2011. The Basic
and Additional Rent on Suites 200, 220, and 350, for the period September 1st,
2008 to July 31st, 2011 (provided Tenant has exercised its option per paragraph
48 of the Lease) shall be at the same rate as Tenant is then paying on the Core
Space.

4. BASIC RENT

The Basic Rent, commencing upon the Effective Date for each of
the respective suites, shall be $2.75 per square foot per month multiplied by
the square footage leased, as follows:



|         
|---------
|Suite    
|         
|200220350

The Basic Rent described above shall be adjusted August 8th,
1998 and annually thereafter, in the same manner and upon the same date and with
the same limitations as described in paragraph 38 of the Lease.



Notwithstanding anything herein to the contrary, for each of
the Suites 200, 220, and 350, Landlord hereby grants Tenant two months Basic
Rent abatement on such suite. Such Basic Rent Abatement shall be granted to
Tenant irrespective whether Tenant occupies the Premises or not during the two
month period immediately following the Effective Date for each Suite. For
example, if the Effective Date for Suite 200 were June 16th, 1998, Tenant's
lease on Suite 200 would commence June 16th, 1998, and the Basic Rent described
above for Suite 200 would commence August 16th, 1998.

5. ADDITIONAL RENT

For calendar year 1998, commencing upon the Effective Date for
each Suite, Tenant shall pay $0.62 per square foot per month as payment for
Tenant's proportionate share of the expenses of operation, management, and
maintenance of Tenant's Premises. Therefore upon the Effective Date for each
suite Tenant's Additional Rent is as follows:



|         
|---------
|Suite    
|         
|200220350

6. AS-IS

Tenant agrees to lease each suite hereunder in an "as- is"
condition, and any alteration or modification to the Premises shall be made in
accordance with paragraphs 8 & 9 of the Lease at Tenant's sole cost and
expense and shall not delay the commencement of Lease for each of the Suites nor
delay the payments of rent.

7. PARKING

On the Effective Date for each Suite, Tenant's total parking
allocation shall be increased as follows:

Suite 200    25 spacesSuite 220    4 spacesSuite 350    22 spaces

8. NO BROKERS

Landlord and Tenant mutually acknowledge that neither Landlord
nor Tenant have had any dealings with any real estate brokers or agents in
connection with the negotiation of this Fifth Amendment of Lease which has
resulted in any obligation to pay a leasing commission.

9. LEASE IN FULL FORCE AND EFFECT

Except as herein and modified the Lease shall remain in full
force and effect.

IN WITNESS WHEREOF, the parties have signed this Fifth
Amendment of Lease, which for reference purposes shall be deemed to have been
dated as the date above written.

|LANDLORD:                                        | TENANT:                                                      
|------------------------------------------------ | -------------------------------------------------------------
|CROSSROADS ASSOCIATES, and
CLOCKTOWER ASSOCIATES | SIEBEL SYSTEMS, Inc., a
        California Corporation       
|/s/ Boyd Smith
	Title Partner                    | /s/ Kevin A. Johnson
      TitleVice President, Legal Affairs

---

|[Crossroads Logo] | 1875 SOUTH GRANT STREET
      SUITE 100
      SAN MATEO, CALIFORNIA 94402
      (415) 571-5433
|----------------- | ----------------------------------------------------------------------------------------------





August 25, 1998





Ms. Linda JansenSiebel Systems, Inc.1855 South Grant
StreetSan Mateo, CA 94402

RE: SIEBEL SYSTEM, INC. - LEASE AGREEMENT

Dear Ms. Jansen:

As you know, there are several typographical errors in the
Fifth Amendment of Lease. While the total square footage is correct,
clarification is necessary with respect to Suite 200. Therefore, Landlord and
Tenant do herein agree to the following corrections:



PARAGRAPH 1.(a) Suite 200

Comprising 8,077 square feet of rentable space, including Tenant's prorata
share of Building common areas, located on the second floor and as further
described in red on Exhibit "A".

PARAGRAPH 4. BASIC RENT

This paragraph remains unchanged, except for the following change to the
Basic Rent Schedule:



|     
|-----
|Suite
|     
|200  

PARAGRAPH 5. ADDITIONAL RENT

This paragraph remains unchanged, except for the following change to the
Additional Rent Schedule:



|     
|-----
|Suite
|     
|200  

Sincerely,

/s/ Peter KlaymanPeter
Klayman

---

SIXTH AMENDMENT OF LEASE

This Sixth Amendment of Lease is made and entered into this
16th day of September, 1998, by and between Crossroads Associates and Clocktower
Associates (Landlord), and Siebel Systems, Inc. a California Corporation
(Tenant).

RECITALS

A. WHEREAS, Landlord and Tenant entered into a Lease dated June
4th, 1996, (the Lease) for the lease of approximately 66,426 gross square feet
of space located in the five story Building located at 1855 South Grant Street,
San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenant's option to lease the fourth floor of the Building located at 1875 South
Grant Street, San Mateo, San Mateo County, California (and hereinafter referred
to as the 1875 Building) and by letter dated December 17th, 1996, Tenant
exercised Tenant's option to lease the tenth floor of the 1875 Building; and

C. WHEREAS, by First Amendment of Lease dated March 17, 1997Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of the 1875
Building, commencing April 1st, 1997, contingent upon Landlord obtaining a lease
termination agreement with California Federal Bank, which lease termination
agreement was not obtained thereby rendering the First Amendment of Lease void;
and

D. WHEREAS, by Second Amendment of Lease dated March 19, 1997
Tenant leased an additional 12,926 gross square feet of space located on the
first floor of the 1875 Building; and

E. WHEREAS, by letter dated May 23, 1997, Tenant exercised
Tenant's Option to lease the ninth floor of the 1875 Building, and by letter
dated July 28th, 1997 Tenant exercised Tenant's Option to lease the Eighth floor
of the 1875 Building, thereby bringing Tenant's total leased area (subject to
the Ninth floor becoming available) to 150,160 gross square feet of space;
and

F. WHEREAS, by Third Amendment of Lease dated September 1st,
1997 Landlord and Tenant agreed to an early commencement of lease for Suite 130,
in the 1875 Building, such that the Suite 130 Lease commenced September 1st,
1997.

G. WHEREAS, by Fourth Amendment of Lease dated April 2nd, 1998,
Landlord and Tenant agreed that Landlord will allow Tenant to make certain
improvements to Tenant's Premises in the 1875 Building and Tenant further agreed
to additional compensation for additional parking.

H. WHEREAS, Bay Networks exercised its option to extend its
lease on the ninth floor of the 1875 Building, thereby making Tenant's exercise
of option to lease the ninth floor void and therefore bringing Tenant's total
leased area to 132,458 square feet.

I. WHEREAS, by Fifth Amendment of Lease dated May 8, 1998, in
the 1875 Building, Tenant leased an additional 9,453 square feet on the second
floor and 6,973 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 148,884 square feet.

J. WHEREAS, in the 1875 Building, Tenant now desires to lease
an additional 7,113 square feet on the fifth floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 155,997 square feet.

NOW, THEREFORE, in consideration of the foregoing and other
good and valuable consideration, receipt of which is hereby acknowledged,
Landlord and Tenant agree as follows:

1. The area to be leased hereunder shall hereinafter be
referred to as "Suite 500" and is described as follows: 7,113 rentable square
feet of space, which includes Tenant's prorata share of Building common areas,
located on the fifth floor of the Building located at 1875 South Grant Street,
San Mateo, San Mateo County, California and as further outlined in red on
Exhibit "A".

2. EFFECTIVE DATE

The "Effective Date" for the commencement of Lease for Suite
500 shall hereinafter be defined as March 1, 1999.

3. TERM

The Term of Lease for Suite 500 shall commence upon the
Effective Date and shall terminate August 31st, 2008. Landlord and Tenant each
acknowledge that the expiration date of the term of Lease for Suite 500 is
different from the expiration date of the term of lease for the 1855 Building
and The "Core Space" (as defined in Paragraph 3 of the Fifth Amendment of
Lease). In the event the term of Tenant's lease for the Core Space expires and
Tenant vacates the Core Space, nevertheless, the term of lease for Suite 500
leased hereunder shall expire August 31st, 2008 and all the terms and conditions
of the Lease shall remain in full force and effect and shall pertain to the
space leased under this Sixth Amendment of Lease. Furthermore, it is hereby
agreed that the Lease for Suite 500 shall be subject to the Option to Extend
granted to Tenant per paragraph 48 of the Lease. In the event that Tenant
exercises its option to extend the Lease on the Core Space such that the Lease
for the Core Space is extended to July 31st, 2011, then the Lease for Suite 500
shall automatically be extended from August 31st, 2008 to July 31st, 2011. The
Basic and Additional Rent on Suite 500 for the period September 1st, 2008 to
July 31st, 2011 (provided Tenant has exercised its option per paragraph 48 of
the Lease) shall be at the same rate as Tenant is then paying on the Core
Space.

4. BASIC RENT

Commencing upon the Effective Date, Tenant's monthly Basic Rent
for Suite 500 shall be 7,113 s.f. x $2.90 = $20,627.70 per month. This amount
shall be adjusted August 8th, 1999 and annually thereafter, in the same manner
and upon the same date and with the same limitations as described in Paragraph
38 of the Lease.

Notwithstanding anything herein to the contrary, for Suite 500,
Landlord hereby grants Tenant two months Basic Rent abatement on such suite.
Such Basic Rent Abatement shall be granted to Tenant irrespective whether Tenant
occupies the Premises or not during the two month period immediately following
the Effective Date. For example, the Effective Date for Suite 500 is March 1st,
1999, Tenant's lease on Suite 500 will commence March 1st, 1999, and the Basic
Rent described above for Suite 500 will commence May 1st, 1999.

5. ADDITIONAL RENT

Commencing upon the Effective Date, Tenant's Additional Rent as
described in Paragraph 4D of the Lease shall be the then current rate being
charged to tenants occupying Building 1875 and shall continue to be adjusted per
the terms and conditions of Paragraph 4D.

6. AS-IS

Tenant agrees to lease suite 500 hereunder in an "as-is"
condition, and any alteration or modification to the Premises shall be made in
accordance with paragraphs 8 & 9 of the Lease at Tenant's sole cost and
expense and shall not delay the commencement of Lease for Suite 500 nor delay
the payment of rent.

7. PARKING

Upon the Effective Date for Suite 500, Tenant's total parking allocation
shall be increased by 22 spaces.

8. NO BROKERS

Landlord and Tenant mutually acknowledge that neither Landlord
nor Tenant have had any dealings with any real estate brokers or agents in
connection with the negotiation of this Sixth Amendment of Lease which has
resulted in any obligation to pay a leasing commission.

9. LEASE IN FULL FORCE AND EFFECT

Except as herein and modified the Lease shall remain in full force and
effect.

IN WITNESS WHEREOF, the parties have signed this Fifth Amendment of Lease,
which for reference purposes shall be deemed to have been dated as the date
above written.

|LANDLORD:                                        | TENANT:                                                
|------------------------------------------------ | -------------------------------------------------------
|CROSSROADS ASSOCIATES, and
CLOCKTOWER ASSOCIATES | SIEBEL SYSTEMS, Inc., a
        Delaware Corporation   
|/s/ Boyd Smith
	Title Partner                    | /s/ Jeffrey T. Amann
      TitleDirector, Legal Affairs

---

SEVENTH AMENDMENT OF LEASE



This Seventh Amendment of Lease is made and entered into this
1st day of December, 1998, by and between Crossroads Associates and Clocktower
Associates (Landlord), and Siebel Systems, Inc. a California Corporation
(Tenant).

RECITALS

A. WHEREAS, Landlord and Tenant entered into a Lease dated June
4th, 1996, (the Lease) for the lease of approximately 66,426 gross square feet
of space located in the five story Building located at 1855 South Grant Street,
San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenant's option to lease the fourth floor of the Building located at 1875 South
Grant Street, San Mateo, San Mateo County, California (and hereinafter referred
to as the 1875 Building) and by letter dated December 17th, 1996, Tenant
exercised Tenant's option to lease the tenth floor of the 1875 Building; and

C. WHEREAS, by First Amendment of Lease dated March 17, 1997
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of the 1875
Building, commencing April 1st, 1997, contingent upon Landlord obtaining a lease
termination agreement with California Federal Bank, which lease termination
agreement was not obtained thereby rendering the First Amendment of Lease void;
and

D. WHEREAS, by Second Amendment of Lease dated March 19, 1997
Tenant leased an additional 12,926 gross square feet of space located on the
first floor of the 1875 Building; and

E. WHEREAS, by letter dated May 23, 1997, Tenant exercised
Tenant's Option to lease the ninth floor of the 1875 Building, and by letter
dated July 28th, 1997 Tenant exercised Tenant's Option to lease the Eighth floor
of the 1875 Building, thereby bringing Tenants total leased area (subject to the
Ninth floor becoming available) to 150,160 gross square feet of space; and

F. WHEREAS, by Third Amendment of Lease dated September 1st,
1997 Landlord and Tenant agreed to an early commencement of lease for Suite 130,
in the 1875 Building, such that the Suite 130 Lease commenced September 1st,
1997.

G. WHEREAS, by Fourth Amendment of Lease dated April 2nd, 1998,
Landlord and Tenant agreed that Landlord will allow Tenant to make certain
improvements to Tenant's Premises in the 1875 Building and Tenant further agreed
to additional compensation for additional parking.

H. WHEREAS, Bay Networks exercised its option to extend its
lease on the ninth floor of the 1875 Building, thereby making Tenant's exercise
of option to lease the ninth floor void and therefore bringing Tenant's total
leased area to 132,458 square feet.

I. WHEREAS, by Fifth Amendment of Lease dated May 8, 1998, in
the 1875 Building, Tenant leased an additional 9,453 square feet on the second
floor and 6,973 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 148,884 square feet.

J. WHEREAS, by Sixth Amendment of Lease dated September 16,
1998, in the 1875 Building, Tenant leased an additional 7,113 square feet on the
fifth floor (which includes Tenant's proportionate share of building common
areas) and which space was further identified as Suite 500, thereby bringing
Tenant's total leased area to 155,997 square feet.

K. WHEREAS, Tenant's lease of Suite 500 has an "Effective Date"
for the commencement of Lease of March 1, 1999, and Tenant now desires to
commence the Lease for Suite 500 at an earlier "Effective Date" as provided for
herein.

NOW, THEREFORE, in consideration of the foregoing and other
good and valuable consideration, receipt of which is hereby acknowledged,
Landlord and Tenant agree as follows:



1. Tenant hereby acknowledges that Suite 500 is currently
leased to HCIA Inc., as successor-in-interest to Datis Corporation, A California
Corporation ("HCIA") with a lease expiration date of February 28, 1999.
Landlord's ability to provide Tenant an earlier "Effective Date" for Suite 500
is contingent upon Landlord entering into, in Landlord's sole opinion, an
acceptable Early Lease Termination Agreement with HCIA. In the event Landlord
does not enter into such an Early Lease Termination Agreement with respect to
Suite 500, then the provisions of this Seventh Amendment of Lease shall be void
and of no force and effect between the parties and neither Landlord nor Tenant
shall be liable to one another for having entered into this Seventh Amendment of
Lease. All other terms and conditions of the Lease shall remain in full force
and effect and Tenant's "Effective Date" for Suite 500 shall be as provided for
in the Sixth Amendment of Lease, and therefore shall be March 1, 1999.

2. EFFECTIVE DATE

The "Effective Date" for the commencement of Tenant's Lease for
Suite 500 shall hereinafter be defined as the date which is one day immediately
following the Termination Date of the HCIA Lease for Suite 500, but in no event
shall the Effective Date be later than March 1, 1999. Except for the
commencement date of Lease, all other terms and conditions of Tenant's lease of
Suite 500 shall be as provided in the Sixth Amendment.

3. BASIC RENT

Commencing upon the Effective Date, Tenant's monthly Basic Rent
for Suite 500 shall be 7,113 s.f. x $2.90 = $20,627.70 per month. This amount
shall be adjusted August 8th, 1999 and annually thereafter, in the same manner
and upon the same date and with the same limitations as described in Paragraph
38 of the Lease.

Notwithstanding anything herein to the contrary, for Suite 500,
Landlord hereby grants Tenant two months Basic Rent abatement on such suite.
Such Basic Rent Abatement shall be granted to Tenant irrespective whether Tenant
occupies the Premises or not during the two month period immediately following
the Effective Date. For example, if the "Effective Date" as provided for herein
becomes December 15, 1998, Tenant's lease on Suite 500 will commence December
15, 1998 and the Basic Rent described above for Suite 500 will commence February
15, 1999.

4. ADDITIONAL RENT

Commencing upon the Effective Date, Tenant's Additional Rent as
described in Paragraph 4D of the Lease shall be the then current rate being
charged to tenants occupying Building 1875 and shall continue to be adjusted per
the terms and conditions of Paragraph 4D.

5. LEASE IN FULL FORCE AND EFFECT

Except as herein and modified, the Lease shall remain in full
force and effect.

IN WITNESS WHEREOF, the parties have signed this Seventh
Amendment of Lease, which for reference purposes shall be deemed to have been
dated as the date above written.

|LANDLORD:                                        | TENANT:                                                
|------------------------------------------------ | -------------------------------------------------------
|CROSSROADS ASSOCIATES, and
CLOCKTOWER ASSOCIATES | SIEBEL SYSTEMS, Inc., a
        Delaware Corporation   
|/s/ Boyd Smith
	Title Partner                    | /s/ Jeffrey T. Amann
      TitleDirector, Legal Affairs

---

EIGHTH AMENDMENT OF LEASE

This Eighth Amendment of Lease is made and entered into this
15th day of January, 1999, by and between Crossroads Associates and Clocktower
Associates (Landlord), and Siebel Systems, Inc. a Delaware Corporation
(Tenant).

RECITALS

A. WHEREAS, Landlord and Tenant entered into a Lease dated June
4th, 1996, (the Lease) for the lease of approximately 66,426 gross square feet
of space located in the five story Building located at 1855 South Grant Street,
San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenant's option to lease the fourth floor of the Building located at 1875 South
Grant Street, San Mateo, San Mateo County, California (and hereinafter referred
to as the 1875 Building) and by letter dated December 17th, 1996, Tenant
exercised Tenant's option to lease the tenth floor of the 1875 Building; and

C. WHEREAS, by First Amendment of Lease dated March 17, 1997
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of the 1875
Building, commencing April 1st, 1997, contingent upon Landlord obtaining a lease
termination agreement with California Federal Bank, which lease termination
agreement was not obtained thereby rendering the First Amendment of Lease void;
and

D. WHEREAS, by Second Amendment of Lease dated March 19, 1997
Tenant leased an additional 12,926 gross square feet of space located on the
first floor of the 1875 Building; and

E. WHEREAS, by letter dated May 23, 1997, Tenant exercised
Tenant's Option to lease the ninth floor of the 1875 Building, and by letter
dated July 28th, 1997 Tenant exercised Tenant's Option to lease the Eighth floor
of the 1875 Building, thereby bringing Tenant's total leased area (subject to
the Ninth floor becoming available) to 150,160 gross square feet of space;
and

F. WHEREAS, by Third Amendment of Lease dated September 1st,
1997 Landlord and Tenant agreed to an early commencement of lease for Suite 130,
in the 1875 Building, such that the Suite 130 Lease commenced September 1st,
1997.

G. WHEREAS, by Fourth Amendment of Lease dated April 2nd, 1998,
Landlord and Tenant agreed that Landlord will allow Tenant to make certain
improvements to Tenant's Premises in the 1875 Building and Tenant further agreed
to additional compensation for additional parking.

H. WHEREAS, Bay Networks exercised its option to extend its
lease on the ninth floor of the 1875 Building, thereby making Tenant's exercise
of option to lease the ninth floor void and therefore bringing Tenant's total
leased area to 132,458 square feet.

I. WHEREAS, by Fifth Amendment of Lease dated May 8, 1998, in
the 1875 Building, Tenant leased an additional 9,453 square feet on the second
floor and 6,973 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 148,884 square feet.

J. WHEREAS, by Sixth Amendment of Lease dated September 16,
1998, in the 1875 Building, Tenant leased an additional 7,113 square feet on the
fifth floor (which includes Tenant's proportionate share of building common
areas) and which space was further identified as Suite 500, thereby bringing
Tenant's total leased area to 155,997 square feet.

K. WHEREAS, by Seventh Amendment of Lease dated December 1,
1998, Tenant agreed to lease Suite 500 prior to March 1, 1999 in the event it
became available and Tenant's lease of Suite 500 commenced December 29,
1998.

L. WHEREAS, in the 1875 Building Tenant now desires to lease an
additional 810 square feet on the second floor, an additional 3104 square feet
on the third floor (which square footage includes Tenant's proportionate share
of building common areas), and convert and include Tenant's separate Lease of
1184 square feet on the third floor into this Lease, thereby bringing Tenant's
total leased area to 161,095 square feet.

NOW, THEREFORE, in consideration of the foregoing and other
good and valuable consideration, receipt of which is hereby acknowledged,
Landlord and Tenant agree as follows:

1. The areas to be leased hereunder are all located in the
Building located at 1875 South Grant Street, San Mateo, San Mateo County,
California and are further described as follows:

a) Suite 250

Comprising 810 gross square feet of space, including Tenant's
prorata share of Building common areas, located on the second floor and as
further described in red on Exhibit "Al".

b) Suite 310A&B

Comprising 1,184 gross square feet of space, which includes
Tenant's prorata share of Building common areas, located on the third floor and
as further outlined in red on Exhibit "A2".

c) Suite 320

Comprising 3,104 gross square feet of space, which includes
Tenant's prorata share of Building common areas, located on the third floor and
as further outlined in red on Exhibit "A3".

Tenant hereby acknowledges that under a separate lease
agreement Suite 310A&B is currently leased by Tenant through March 31, 1999.
The other two suites to be leased hereunder, Suites 250 and 320, are currently
leased to RAC Enterprises. Tenant's Lease of Suite 250 and Suite 320 are
contingent upon Landlord entering into, in Landlord's sole opinion, an
acceptable Lease Termination Agreement with RAC Enterprises. In the event
Landlord does not enter into such a lease termination agreement then the
provisions of this Eighth Amendment of Lease applicable to Suites 250 and 320
shall be void and of no force and effect between the parties and neither
Landlord nor Tenant shall be liable to one another for having entered into this
Eighth Amendment of Lease with respect to such space. All other terms and
conditions of the Lease, including the other terms and conditions of this Eighth
Amendment of Lease, shall remain in full force and effect.

2. EFFECTIVE DATE

Subject to the contingency in paragraph 1 above, the "Effective
Date" for the commencement of Lease for Suites 250, 310A&B and 320 shall
hereinafter be defined as April 1, 1999.

3. TERM

Subject to the contingency in paragraph 1 above, commencing
upon the Effective Date Landlord agrees to lease to Tenant and Tenant agrees to
lease and hire from Landlord Suites 310 A & B, 250, and 320. The Term of
Lease for Suites 250, 310A&B and 320 shall terminate August 31st, 2008.
Landlord and Tenant each acknowledge that the expiration date of the term of
Lease for Suites 250, 310A&B, and 320 leased hereunder is different from the
expiration date of the term of lease for the 1855. Building and The "Core Space"
(as defined in Paragraph 3 of the Fifth Amendment of Lease). In the event the
term of Tenant's lease for the Core Space expires and Tenant vacates the Core
Space, nevertheless, the term of lease for Suites 250, 310A&B, and 320
leased hereunder shall expire August 31st, 2008 and all the terms and conditions
of the Lease shall remain in full force and effect and shall pertain to the
space leased under this

Eighth Amendment of Lease. Furthermore, it is hereby agreed
that the Lease for Suites 250, 310A&B, and 320 shall be subject to the
Option to Extend granted to Tenant per paragraph 48 of the Lease. In the event
that Tenant exercises its option to extend the Lease on the Core Space such that
the Lease for the Core Space is extended to July 31st, 2011, then the Lease for
Suites 250, 310A&B, and 320 shall automatically be extended from August
31st, 2008 to July 31st, 2011. The Basic and Additional Rent on Suites 250,
310A&B, and 320 for the period September 1st, 2008 to July 31st, 2011
(provided Tenant has exercised its option per paragraph 48 of the Lease) shall
be at the same rate as Tenant is then paying on the Core Space.

4. BASIC RENT

The Basic Rent, commencing upon the Effective Date for each of
the respective suites, shall be $2.90 per square foot per month multiplied by
the square footage leased, as follows:



|            
|------------
|Suite       
|            
|250310A&B320

The Basic Rent described above shall be adjusted August 8th,
1999 and annually thereafter, in the same manner and upon the same date and with
the same limitations as described in paragraph 38 of the Lease.

Notwithstanding anything herein to the contrary, for Suites 250
and 320, Landlord hereby grants Tenant two months Basic Rent abatement for each
suite. Such Basic Rent Abatement shall be granted to Tenant irrespective whether
Tenant occupies the Premises or not during the two month period immediately
following the Effective Date for each Suite. For example, the Effective Date for
Suites 250 and 320 is April 1st, 1999, Tenant's lease on Suites 250 and 320 will
commence April 1st, 1999, and the Basic Rent described above for Suites 250 and
320 will commence June 1st, 1999.

5. ADDITIONAL RENT

Commencing upon the Effective Date, Tenant's Additional Rent
for each suite, as described in Paragraph 4D of the Lease, shall be the then
current rate per square foot per month being charged to tenants occupying
Building 1875 multiplied by the respective square footages and shall continue to
be adjusted per the terms and conditions of Paragraph 4D.

6. AS-IS

Tenant agrees to lease each suite hereunder in an "as-is" condition, and any
alteration or modification to the Premises shall be made in accordance with
paragraphs 8 & 9 of the Lease at Tenant's sole cost and expense and shall
not delay the commencement of Lease for each of the Suites nor delay the
payments of rent.

7. PARKING

On the Effective Date for each Suite, Tenant's total parking allocation shall
be increased as follows:



|Suite 250    |  | 2 spaces 
|------------ |  | ---------
|Suite 310A&B |  | 3 spaces 
|Suite 320    |  | 10 spaces

8. NO BROKERS

Landlord and Tenant mutually acknowledge that neither Landlord
nor Tenant have had any dealings with any real estate brokers or agents in
connection with the negotiation of this Eighth Amendment of Lease which has
resulted in any obligation to pay a leasing commission.

9. LEASE IN FULL FORCE AND EFFECT

Except as herein and modified the Lease shall remain in full force and
effect.

IN WITNESS WHEREOF, the parties have signed this Eighth
Amendment of Lease, which for reference purposes shall be deemed to have been
dated as the date above written.

|LANDLORD:                                        | TENANT:                                                
|------------------------------------------------ | -------------------------------------------------------
|CROSSROADS ASSOCIATES, and
CLOCKTOWER ASSOCIATES | SIEBEL SYSTEMS, Inc., a
        Delaware Corporation   
|/s/ Boyd Smith
	Title Partner                    | /s/ Jeffrey T. Amann
      TitleDirector, Legal Affairs

---

NINTH AMENDMENT OF LEASE

This Ninth Amendment of Lease is made and entered into this
26th day of January, 1999, by and between Crossroads Associates and Clocktower
Associates (Landlord), and Siebel Systems, Inc. a Delaware Corporation
(Tenant).

RECITALS

A. WHEREAS, Landlord and Tenant entered into a Lease dated June
4th, 1996, (the Lease) for the lease of approximately 66,426 gross square feet
of space located in the five story Building located at 1855 South Grant Street,
San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenants option to lease the fourth floor of the Building located at 1875 South
Grant Street, San Mateo, San Mateo County, California (and hereinafter referred
to as the 1875 Building) and by letter dated December 17th, 1996, Tenant
exercised Tenants option to lease the tenth floor of the 1875 Building; and

C. WHEREAS, by First Amendment of Lease dated March 17, 1997
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of the 1875
Building, commencing April 1st, 1997, contingent upon Landlord obtaining a lease
termination agreement with California Federal Bank, which lease termination
agreement was not obtained thereby rendering the First Amendment of Lease void;
and

D. WHEREAS, by Second Amendment of Lease dated March 19, 1997
Tenant leased an additional 12,926 gross square feet of space located on the
first floor of the 1875 Building; and

E. WHEREAS, by letter dated May 23, 1997, Tenant exercised
Tenant's Option to lease the ninth floor of the 1875 Building, and by letter
dated July 28th, 1997 Tenant exercised Tenant's Option to lease the Eighth floor
of the 1875 Building, thereby bringing Tenant's total leased area (subject to
the Ninth floor becoming available) to 150,160 gross square feet of space;
and

F. WHEREAS, by Third Amendment of Lease dated September 1st,
1997 Landlord and Tenant agreed to an early commencement of lease for Suite 130,
in the 1875 Building, such that the Suite 130 Lease commenced September 1st,
1997.

G. WHEREAS, by Fourth Amendment of Lease dated April 2nd, 1998,
Landlord and Tenant agreed that Landlord will allow Tenant to make certain
improvements to Tenant's Premises in the 1875 Building and Tenant further agreed
to additional compensation for additional parking.

H. WHEREAS, Bay Networks exercised its option to extend its
lease on the ninth floor of the 1875 Building, thereby making Tenant's exercise
of option to lease the ninth floor void and therefore bringing Tenant's total
leased area to 132,458 square feet.

I. WHEREAS, by Fifth Amendment of Lease dated May 8, 1998, in
the 1875 Building, Tenant leased an additional 9,453 square feet on the second
floor and 6,973 square feet on the third floor which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 148,884 square feet.

J. WHEREAS, by Sixth Amendment of Lease dated September 16,
1998, in the 1875 Building, Tenant leased an additional 7,113 square feet on the
fifth floor (which includes Tenant's proportionate share of building common
areas) and which space was further identified as Suite 500, thereby bringing
Tenant's total leased area to 155,997 square feet.

K. WHEREAS, by Seventh Amendment of Lease dated December 1,
1998, Tenant agreed to lease Suite 500 prior to March 1, 1999 in the event it
became available and Tenant's lease of Suite 500 commenced December 29,
1998.

L. WHEREAS, by Eighth Amendment of Lease dated January 15, 1999
in the 1875 Building, Tenant leased an additional 810 square feet on the second
floor and 4,288 square feet on the third floor(which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 161,095 square feet.

M. WHEREAS, in the 1875 Building Tenant now desires to lease an
additional 5,221 square feet on the sixth floor, an additional 2,695 square feet
on the seventh floor (which square footage includes Tenant's proportionate share
of building common areas), thereby bringing Tenant's total leased area to
169,011 square feet.

NOW, THEREFORE, in consideration of the foregoing and other
good and valuable consideration, receipt of which is hereby acknowledged,
Landlord and Tenant agree as follows:

1. The areas to be leased hereunder are all located in the
Building located at 1875 South Grant Street, San Mateo, San Mateo County,
California and are further described as follows:



a) Suite 650

Comprising 5,221 gross square feet of space, including Tenant's
prorata share of Building common areas, located on the fifth floor and as
further described in red on Exhibit "Al".

b) Suite 770

Comprising 2,695 gross square feet of space, which includes
Tenant's prorata share of Building common areas, located on the seventh floor
and as further outlined in red on Exhibit "A2".

Tenant hereby acknowledges that the two suites to be leased
hereunder, Suites 650 and 770, are currently leased to SUNTERRA CORPORATION.
Tenant's Lease of Suite 650 and Suite 770 is contingent upon Landlord entering
into, in Landlord's sole opinion, an acceptable Lease Termination Agreement with
SUNTERRA CORPORATION by February 20, 1999. In the event Landlord does not enter
into such a lease termination agreement then this Ninth Amendment of Lease shall
be void and of no force and effect between the parties and neither Landlord nor
Tenant shall be liable to one another for having entered into this Ninth
Amendment of Lease and the Lease shall remain in full force and effect.

2. EFFECTIVE DATE

Subject to Paragraph 1 above, the Effective Dates shall be as
follows:

(a) Suite 650 - March 1, 1999
(b) Suite 770 - April 1, 1999

3. TERM

Subject to the contingency in paragraph 1 above, commencing
upon the respective Effective Dates Landlord agrees to lease to Tenant and
Tenant agrees to lease and hire from Landlord Suites 650 and 770. The Term of
Lease for Suites 650 and 770 shall terminate August 31st, 2008. Landlord and
Tenant each acknowledge that the expiration date of the term of Lease for Suites
650 and 770 leased hereunder is different from the expiration date of the term
of lease for the 1855 Building and The "Core Space" (as defined in Paragraph 3
of the Fifth Amendment of Lease). In the event the term of Tenant's lease for
the Core Space expires and Tenant vacates the Core Space, nevertheless, the term
of lease for Suites 650 and 770 leased hereunder shall expire August 31st, 2008
and all the terms and conditions of the Lease shall remain in full force and
effect and shall pertain to the space leased under this Ninth Amendment of
Lease. Furthermore, it is hereby agreed that the Lease for Suites 650 and 770
shall be subject to the Option to Extend granted to Tenant per paragraph 48 of
the Lease. In the event that Tenant exercises its option to extend the Lease on
the Core Space such that the Lease for the Core Space is extended to July 31st,
2011, then the Lease for Suites 650 and 770 shall automatically be extended from
August 31st, 2008 to July 31st, 2011. The Basic and Additional Rent on Suites
650 and 770 for the period September 1st, 2008 to July 31st, 2011 (provided
Tenant has exercised its option per paragraph 48 of the Lease) shall be at the
same rate as Tenant is then paying on the Core Space.

4. BASIC RENT

The Basic Rent, commencing upon the Effective Date for each of
the respective suites, shall be $2.90 per square foot per month multiplied by
the square footage leased, as follows:





|      
|------
|Suite 
|      
|650770

The Basic Rent described above shall be adjusted August 8th,
1999 and annually thereafter, in the same manner and upon the same date and with
the same limitations as described in paragraph 38 of the Lease.



Notwithstanding anything herein to the contrary, for Suites 650
and 770, Landlord hereby grants Tenant two months Basic Rent abatement for each
suite. Such Basic Rent Abatement shall be granted to Tenant irrespective whether
Tenant occupies the Premises or not during the two month period immediately
following the Effective Date for each Suite. For example, the Effective Date for
Suite 650 is March 1st, 1999, Tenant's lease on Suite 650 will commence March
1st, 1999, and the Basic Rent described above for Suite 650 will commence May
1st, 1999.

5. ADDITIONAL RENT

Commencing upon the respective Effective Dates, Tenant's
Additional Rent for each suite, as described in Paragraph 4D of the Lease, shall
be the then current rate per square foot per month being charged to tenants
occupying Building 1875 multiplied by the respective square footages and shall
continue to be adjusted per the terms and conditions of Paragraph 4D.

6. AS-IS

Tenant agrees to lease each suite hereunder in an "as- is"
condition, and any alteration or modification to the Premises shall be made in
accordance with paragraphs 8 & 9 of the Lease at Tenant's sole cost and
expense and shall not delay the commencement of Lease for each of the Suites nor
delay the payments of rent.

7. PARKING

On the Effective Date for each Suite, Tenant's total parking
allocation shall be increased as follows:



|Suite 650 | 16 spaces
|--------- | ---------
|Suite 770 | 8 spaces 

8. NO BROKERS

Landlord and Tenant mutually acknowledge that neither Landlord
nor Tenant have had any dealings with any real estate brokers or agents in
connection with the negotiation of this Ninth Amendment of Lease which has
resulted in any obligation to pay a leasing commission.

9. LEASE IN FULL FORCE AND EFFECT

Except as herein and modified the Lease shall remain in full
force and effect.

IN WITNESS WHEREOF, the parties have signed this Ninth
Amendment of Lease, which for reference purposes shall be deemed to have been
dated as the date above written.

|LANDLORD:                                        | TENANT:                                                
|------------------------------------------------ | -------------------------------------------------------
|CROSSROADS ASSOCIATES, and
CLOCKTOWER ASSOCIATES | SIEBEL SYSTEMS, Inc., a
        Delaware Corporation   
|/s/ Boyd Smith
	Title Partner                    | /s/ Jeffrey T. Amann
      TitleDirector, Legal Affairs

---

TENTH AMENDMENT OF LEASE



This Tenth Amendment of Lease is made and entered into this
25th day of February, 1999, by and between Crossroads Associates and Clocktower
Associates (Landlord), and Siebel Systems, Inc. a Delaware Corporation
(Tenant).

RECITALS

A. WHEREAS, Landlord and Tenant entered into a Lease dated June
4th, 1996, (the Lease) for the lease of approximately 66,426 gross square feet
of space located in the five story Building located at 1855 South Grant Street,
San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenant's option to lease the fourth floor of the Building located at 1875 South
Grant Street, San Mateo, San Mateo County, California (and hereinafter referred
to as the 1875 Building) and by letter dated December 17th, 1996, Tenant
exercised Tenant's option to lease the tenth floor of the 1875 Building; and

C. WHEREAS, by First Amendment of Lease dated March 17, 1997
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of the 1875
Building, commencing April 1st, 1997, contingent upon Landlord obtaining a lease
termination agreement with California Federal Bank, which lease termination
agreement was not obtained thereby rendering the First Amendment of Lease void;
and

D. WHEREAS, by Second Amendment of Lease dated March 19, 1997
Tenant leased an additional 12,926 gross square feet of space located on the
first floor of the 1875 Building; and

E. WHEREAS, by letter dated May 23, 1997, Tenant exercised
Tenant's Option to lease the ninth floor of the 1875 Building, and by letter
dated July 28th, 1997 Tenant exercised Tenant's Option to lease the Eighth floor
of the 1875 Building, thereby bringing Tenant's total leased area (subject to
the Ninth floor becoming available) to 150,160 gross square feet of space;
and

F. WHEREAS, by Third Amendment of Lease dated September 1st,
1997 Landlord and Tenant agreed to an early commencement of lease for Suite 130,
in the 1875 Building, such that the Suite 130 Lease commenced September 1st,
1997.

G. WHEREAS, by Fourth Amendment of Lease dated April 2nd, 1998,
Landlord and Tenant agreed that Landlord will allow Tenant to make certain
improvements to Tenant's Premises in the 1875 Building and Tenant further agreed
to additional compensation for additional parking.

H. WHEREAS, Bay Networks exercised its option to extend its
lease on the ninth floor of the 1875 Building, thereby making Tenant's exercise
of option to lease the ninth floor void and therefore bringing Tenant's total
leased area to 132,458 square feet.

I. WHEREAS, by Fifth Amendment of Lease dated May 8, 1998, in
the 1875 Building, Tenant leased an additional 9,453 square feet on the second
floor and 6,973 square feet on the third floor(which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 148,884 square feet.

J. WHEREAS, by Sixth Amendment of Lease dated September 16,
1998, in the 1875 Building, Tenant leased an additional 7,113 square feet on the
fifth floor (which includes Tenant's proportionate share of building common
areas) and which space was further identified as Suite 500, thereby bringing
Tenant's total leased area to 155,997 square feet.

K. WHEREAS, by Seventh Amendment of Lease dated December
1,1998, Tenant agreed to lease Suite 500 prior to March 1, 1999 in the event it
became available and Tenant's lease of Suite 500 commenced December 29,
1998.

L. WHEREAS, by Eighth Amendment of Lease dated January 15, 1999
in the 1875 Building, Tenant leased an additional 810 square feet on the second
floor and 4,288 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 161,095 square feet.

M. WHEREAS, by Ninth Amendment of Lease dated January 25, 1999
in the 1875 Building, Tenant leased an additional 5,221 square feet on the sixth
floor and 2,695 square feet on the seventh floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 169,011 square feet.

N. WHEREAS, in the 1875 Building Tenant now desires to lease an
additional 4,319 square feet on the second floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 173,330 square feet.

NOW, THERFORE, in consideration of the foregoing and other good
and valuable consideration, receipt of which is hereby acknowledged, Landlord
and Tenant agree as follows:

1. The area to be leased hereunder shall hereinafter be
referred to as "Suite 240" and is described as follows: 4,319 gross square feet
of space, which includes Tenant's prorata share of Building common areas,
located on the second floor of the Building located at 1875 South Grant Street,
San Mateo, San Mateo County, California and as further outlined in red on
Exhibit "A".

2. EFFECTIVE DATE

The "Effective Date" for the commencement of Lease for Suite
240 shall hereinafter be defined as July 1, 1999.

3. TERM

The Term of Lease for Suite 240 shall commence upon the
Effective Date and shall terminate August 31st, 2008. Landlord and Tenant each
acknowledge that the expiration date of the term of Lease for Suite 240 is
different from the expiration date of the term of lease for the 1855 Building
and The "Core Space" (as defined in Paragraph 3 of the Fifth Amendment of Lease)
.. In the event the term of Tenant's lease for the Core Space expires and Tenant
vacates the Core Space, nevertheless, the term of lease for Suite 240 leased
hereunder shall expire August 31st, 2008 and all the terms and conditions of the
Lease shall remain in full force and effect and shall pertain to the space
leased under this Tenth Amendment of Lease. Furthermore, it is hereby agreed
that the Lease for Suite 240 shall he subject to the Option to Extend granted to
Tenant per paragraph 48 of the Lease. In the event that Tenant exercises its
option to extend the Lease on the Core Space such that the Lease for the Core
Space is extended to July 31st, 2011, then the Lease for Suite 240 shall
automatically be extended from August 31st, 2008 to July 31st, 2011. The Basic
and Additional Rent on Suite 240 for the period September 1st, 2008 to July
31st, 2011 (provided Tenant has exercised its option per paragraph 48 of the
Lease) shall be at the same rate as Tenant is then paying on the Core Space.

4. BASIC RENT

Commencing upon the Effective Date, Tenant's monthly Basic Rent
for Suite 240 shall be 4,319 s.f. x $2.90 = $12,525.10 per month. This amount
shall be adjusted August 8th, 1999 and annually thereafter, in the same manner
and upon the same date and with the same limitations as described in Paragraph
38 of the Lease.

Notwithstanding anything herein to the contrary, for Suite 240,
Landlord hereby grants tenant two months Basic Rent abatement on such suite.
Such Basic Rent Abatement shall be granted to Tenant irrespective whether Tenant
occupies the Premises or not during the two month period immediately following
the Effective Date. For example, the Effective Date for Suite 240 is July 1st,
1999, Tenant's lease on Suite 240 will commence July 1st, 1999, and the Basic
Rent described above for Suite 240 will commence September 1st, 1999.

5. ADDITIONAL RENT

Commencing upon the Effective Date, Tenant's Additional Rent as
described in Paragraph 4D of the Lease shall be the then current rate being
charged to tenants occupying Building 1875 and shall continue to be adjusted per
the terms and conditions of Paragraph 4D.

6. AS-IS

Tenant agrees to lease each suite hereunder in an "as- is"
condition, and any alteration or modification to the Premises shall be made in
accordance with paragraphs 8 & 9 of the Lease at Tenant's sole cost and
expense and shall not delay the commencement of Lease for each of the Suites nor
delay the payments of rent.

7. EARLY OCCUPANCY

In the event that Suite 240 becomes available prior to the
applicable Effective Date, and in the event that Tenant desires to take
possession of Suite 240 prior to the applicable Effective Date, then with
Landlord's permission Tenant may do so. Tenant shall Suite 240 subject to the
Early Occupancy provisions of this Paragraph 7 and Tenant's Early Occupancy
shall be subject to all the terms and conditions of the Lease. In the event that
Suite 240 is available and Tenant so chooses to occupy such space prior to the
Effective Date, then the Basic Rent obligations shall be as stated in paragraph
4 herein with the exception that Tenant shall pay Basic and Additional Rent for
the period of such Early Occupancy prior to the Effective Date. Such Basic and
Additional Rent shall be calculated on a per diem basis for each day of the
period commencing with the date of Early Occupancy to the Effective Date. The
daily rate of Basic and Additional Rent is as indicated in the table
below:

EARLY OCCUPANCY TABLE



|     
|-----
|Suite
|     
|240  

8. PARKING

Upon the Effective Date for Suite 240, Tenant's total parking
allocation shall be increased by 13 spaces.

9. NO BROKERS

Landlord and Tenant mutually acknowledge that neither Landlord
nor Tenant have had any dealings with any real estate brokers or agents in
connection with the negotiation of this Tenth Amendment of Lease which has
resulted in any obligation to pay a leasing commission.

10. LEASE IN FULL FORCE AND EFFECT

Except as herein and modified the Lease shall remain in full
force and effect.

IN WITNESS WHEREOF, the parties have signed this Tenth
Amendment of Lease, which for reference purposes shall be deemed to have been
dated as the date above written.

|LANDLORD:                                        | TENANT:                                                
|------------------------------------------------ | -------------------------------------------------------
|CROSSROADS ASSOCIATES, and
CLOCKTOWER ASSOCIATES | SIEBEL SYSTEMS, Inc., a
        Delaware Corporation   
|/s/ Boyd Smith
	Title Partner                    | /s/ Jeffrey T. Amann
      TitleDirector, Legal Affairs

---

ELEVENTH AMENDMENT OF LEASE

This Eleventh Amendment of Lease is made and entered into this
7th day of April, 1999, by and between Crossroads Associates and Clocktower
Associates (Landlord), and Siebel Systems, Inc. a Delaware Corporation
(Tenant).

RECITALS

A. WHEREAS, Landlord and Tenant entered into a Lease dated June
4th, 1996, (the Lease) for the lease of approximately 66,426 gross square feet
of space located in the five story Building located at 1855 South Grant Street,
San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenants option to lease the fourth floor of the Building located at 1875 South
Grant Street, San Mateo, San Mateo County, California (and hereinafter referred
to as the 1875 Building) and by letter dated December 17th, 1996, Tenant
exercised Tenants option to lease the tenth floor of the 1875 Building; and

C. WHEREAS, by First Amendment of Lease dated March 17, 1997
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of the 1875
Building, commencing April 1st, 1997, contingent upon Landlord obtaining a lease
termination agreement with California Federal Bank, which lease termination
agreement was not obtained thereby rendering the First Amendment of Lease void;
and

D. WHEREAS, by Second Amendment of Lease dated March 19,1997
Tenant leased an additional 12,926 gross square feet of space located on the
first floor of the 1875 Building; and

E. WHEREAS, by letter dated May 23, 1997, Tenant exercised
Tenant's Option to lease the ninth floor of the 1875 Building, and by letter
dated July 28th, 1997 Tenant exercised Tenant's Option to lease the Eighth floor
of the 1875 Building, thereby bringing Tenant's total leased area (subject to
the Ninth floor becoming available) to 150,160 gross square feet of space;
and

F. WHEREAS, by Third Amendment of Lease dated September 1st,
1997 Landlord and Tenant agreed to an early commencement of lease for Suite 130,
in the 1875 Building, such that the Suite 130 Lease commenced September 1st,
1997.

G. WHEREAS, by Fourth Amendment of Lease dated April 2nd,1998,
Landlord and Tenant agreed that Landlord will allow Tenant to make certain
improvements to Tenant's Premises in the 1875 Building and Tenant further agreed
to additional compensation for additional parking.

H. WHEREAS, Bay Networks exercised its option to extend its
lease on the ninth floor of the 1875 Building, thereby making Tenant's exercise
of option to lease the ninth floor void and therefore bringing Tenant's total
leased area to 132,458 square feet.

I. WHEREAS, by Fifth Amendment of Lease dated May 8, 1998, in
the 1875 Building, Tenant leased an additional 9,453 square feet on the second
floor and 6,973 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 148,884 square feet.

J. WHEREAS, by Sixth Amendment of Lease dated September 16,
1998, in the 1875 Building, Tenant leased an additional 7,113 square feet on the
fifth floor (which includes Tenant's proportionate share of building common
areas) and which space was further identified as Suite 500, thereby bringing
Tenant's total leased area to 155,997 square feet.

K. WHEREAS, by Seventh Amendment of Lease dated December 1,
1998, Tenant agreed to lease Suite 500 prior to March 1, 1999 in the event it
became available and Tenant's lease of Suite 500 commenced December 29,
1998.

L. WHEREAS, by Eighth Amendment of Lease dated January 15, 1999
in the 1875 Building, Tenant leased an additional 810 square feet on the second
floor and 4,288 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 161,095 square feet.

M. WHEREAS, by Ninth Amendment of Lease dated January 25, 1999
in the 1875 Building, Tenant leased an additional 5,221 square feet on the sixth
floor and 2,695 square feet on the seventh floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 169,011 square feet.

N. WHEREAS, subject to the execution of the Tenth Amendment of
Lease dated February 25, 1999 in the 1875 Building, Tenant upon execution will
have leased an additional 4,319 square feet on the second floor (which includes
Tenant's proportionate share of building common areas), thereby bringing
Tenant's total leased area to 173,330 square feet.

O. WHEREAS, in the 1825 Building Tenant now desires to lease an
additional 7,509 square feet on the first floor, 11,417 square feet on the fifth
floor, 17,702 on the eighth floor and 17,702 square feet on the ninth floor
(which includes Tenant's proportionate share of building common areas), thereby
bringing Tenant's total leased area to 227,660 square feet.

NOW, THEREFORE, in consideration of the foregoing and other
good and valuable consideration, receipt of which is hereby acknowledged,
Landlord and Tenant agree as follows:

1. The areas to be leased hereunder are all located in the
Building located at 1825 South Grant Street, San Mateo, San Mateo County,
California and are further described as follows:

a) Suite 150

Comprising 7,509 gross square feet of space, which includes
Tenant's prorata share of Building common areas, located on the first floor and
as further described in red on Exhibit "Al".

b) Suite 500

Comprising 11,417 gross square feet of space, which includes
Tenant's prorate share of Building common areas, located on the fifth floor and
as further outlined in red on Exhibit "A2".

c) Suite 800

Comprising 17,702 gross square feet of space, which includes
Tenant's prorate share of Building common areas, located on the eighth floor and
as further outlined in red on Exhibit "A3".

d) Suite 900

Comprising 17,702 gross square feet of space, which includes
Tenant's prorate share of Building common areas, located on the ninth floor and
as further outlined in red on Exhibit "A4".

Tenant hereby acknowledges that all four suites to be leased
hereunder, Suites 150, 500, 800 and 900, are currently leased to VISA. Tenant's
Lease of Suites 150, 500, 800 and 900 is contingent upon Landlord entering into,
in Landlord's sole opinion, an acceptable lease termination agreement with VISA
for the referenced suites. Landlord and VISA have discussed such an acceptable
lease termination agreement, and termination documents have been submitted to
VISA for execution. In the event Landlord and VISA do not enter into such a
lease termination agreement, then the provisions of this Eleventh Amendment of
Lease shall be void and of no force and effect between the parties, neither
Landlord nor Tenant shall be liable to one another for having entered into this
Eleventh Amendment of Lease, and all other terms and conditions of the Lease
shall remain in full force and effect.

2. EFFECTIVE DATE

The Effective Date shall hereinafter be defined as that date
which Landlord shall specify to Tenant in writing as the commencement date of
the term of Lease for thePremises leased per this 11 Amendment. The
Effective date shall not be earlier than November 1, 1999 nor later than January
1, 2000. On or before September 15, 1999, Landlord shall notify Tenant in
writing the specific date that shall be the Effective date.

3. TERM

The Term of Lease for Suites 150, 500, 800 and 900 shall
commence upon the Effective Date and shall terminate October 31, 2009. Landlord
and Tenant each acknowledge that the expiration date of the term of Lease for
Suites 150, 500, 800 and 900 is different from the expiration date of the term
of lease for other space leased by Tenant, including the expiration date of the
term of lease for the 1855 Building and the "Core Space" (as defined in
Paragraph 3 of the Fifth Amendment of Lease). In the event the term of Tenant's
lease for the Core Space and/or the term of Tenant's lease for other space
leased expires and Tenant vacates these spaces, nevertheless, the term of lease
for Suites 150, 500, 800 and 900 leased hereunder shall expire October 31, 2009
and all the terms and conditions of the Lease shall remain in full force and
effect and shall pertain to the space leased under this Eleventh Amendment of
Lease. Furthermore, it is hereby agreed that the Lease for Suites 150, 500, 800
and 900 shall be subject to the Option to Extend granted to Tenant per paragraph
48 of the Lease such that in the event that Tenant exercises its option to
extend the Lease on the Core Space such that the Lease for the Core Space is
extended to July 31st, 2011, then the Lease for Suites 150, 500, 800 and 900
shall automatically be extended from October 31, 2009 to July 31st, 2011. The
Basic and Additional Rent on Suites 150, 500, 800 and 900 for the period
November 1st, 2009 to July 31st, 2011 (provided Tenant has exercised its option
per paragraph 48 of the Lease) shall be at the same rate as Tenant is paying on
the Core Space for that period. As is stated in Paragraph 48 (f), Tenant's
second Option to Extend shall apply to all space then leased by Tenant as of the
date of the exercise of the second option.

4. BASIC RENT

The Basic Rent for the additional space leased per this
Eleventh Amendment, commencing upon the Effective Date, shall be $2.90 per
square foot per month multiplied by the square footage leased, as follows:





|            
|------------
|Suite       
|            
|150500800900

The Basic Rent described above shall be adjusted August 8th,
2000 and annually thereafter, in the same manner and upon the same date and with
the same limitations as described in paragraph 38 of the Lease.

Notwithstanding anything herein to the contrary, for Suites
150, 500, 800 and 900, Landlord hereby grants Tenant two months Basic Rent
abatement for each suite. Such Basic Rent Abatement shall be granted to Tenant
irrespective of whether Tenant occupies the Premises or not during the two month
period immediately following the Effective Date. For example, if the Effective
Date for Suites 150, 500, 800 and 900 is November 1, 1999, Tenant's lease on
Suites 150, 500, 800 and 900 will commence November 1, 1999, and the Basic Rent
described above for Suites 150, 500, 800 and 900 will commence January 1, 2000,
irrespective of Tenant's occupancy.

5. ADDITIONAL RENT

Commencing upon the Effective Date, Tenant's Additional Rent
(as described in Paragraph 4D of the Lease) for each of the suites leased
hereunder shall be the then current rate being charged to tenants occupying the
Building 1825 multiplied by the square footage of each suite and shall continue
to be adjusted per the terms and conditions of Paragraph 4D.

6. AS-IS

Tenant agrees to lease each suite hereunder in an "as-is"
condition, and any alteration or modification to the Premises shall be made in
accordance with paragraphs 8 & 9 of the Lease at Tenant's sole cost and
expense and shall not delay the commencement of Lease for each of the Suites nor
delay the payment of rent.

7. PARKING

On the Effective Date, Tenant's total parking allocation shall
be increased as follows:



|Suite 150 | 23 spaces
|--------- | ---------
|Suite 500 | 36 spaces
|Suite 800 | 56 spaces
|Suite 900 | 56 spaces

8. BROKERS

Landlord has not been represented by any real estate broker(s)
with respect to this transaction and shall not be responsible for any leasing
commission in connection with the negotiation of this Eleventh Amendment of
Lease. Tenant shall hold Landlord harmless from any leasing commission which may
be due to a real estate broker or agent representing Tenant.

9. SIGNS

Paragraph 41 (SIGNS) of the Original Lease is hereby agreed to
be deleted, and the following paragraph is substituted in its entirety:

Exhibit B-1 is a site plan of the Complex. For purposes of this
paragraph the buildings shall be referred to as 1825 (Building One), 1875
(Building Two), and 1855 (Building Three). Within the perimeter outline of each
of the three buildings shown on Exhibit B-1 various building surfaces have been
further identified by Roman Numerals I-VI. An "east-facing sign" will mean a
sign generally facing east toward highway 101, and a "west- facing" sign will
mean a sign generally facing west in the direction of South Grant Street.
Currently there are four building-mounted exterior lighted signs: one east
facing (I) and one west facing (II) SIEBEL sign on building 3 (1855) and one
east facing (III) and one west facing (IV) CROSSROADS sign on building 2 (1875).
These existing signs are indicated on Exhibit B-2.

Landlord's granting Tenant additional signage is subject to
obtaining certain specific approvals from the City of San Mateo, and is subject
to the further conditions as hereinafter described. Any additional Tenant
sign(s) must be constructed and installed at Tenant's sole cost and expense,
including the cost of any applications or fees that must be paid to the City of
San Mateo. All signs must be approved by Landlord and are subject to the review
and must be approved by the City of San Mateo. Any additional sign(s) must use a
lettering size no larger than the existing CROSSROADS signs (III & IV) on
building 2 (1875). Other than the manufacturing and installation costs of any
additional sign(s), Landlord shall allow Tenant's additional sign(s) at no
additional cost. Landlord and Tenant shall fully cooperate with one another in obtaining the approvals from the City of San Mateo for additional signage. The Lease and this Eleventh Amendment(subject to paragraph 1 above) are not contingent upon the obtaining from the City of San Mateo the right to place any additional signage at the Complex, and the Lease and this Eleventh Amendment (subject to paragraph 1 above) shall nevertheless remain in full force and effect without diminution of rent or other offsets.

If at any time Tenant occupies less than 150,000 square feet of
space in the Complex (herein defined as a Diminished Occupancy Condition), and
it is determined with both parties acting in good faith that the Diminished
Occupancy Condition will last more than two years, Landlord shall have the right
to require Tenant to remove the additional sign(s) approved per this paragraph
at Tenant's expense. If so required, or upon Lease termination, Tenant shall
remove such sign(s) within 30 days of Landlord's request and Tenant shall make
all required repairs to restore any damage to the Premises from Tenant's
sign.

It is Landlord and Tenant's intent to obtain approval to place
two additional exterior building-mounted lighted signs on Building One (1825,
locations V & VI) . This shall hereinafter be referred to as plan One. In
the event the City of San Mateo does not approve Plan One, Landlord and Tenant
shall attempt to obtain approval to place one additional exterior
building-mounted lighted sign on Building One (1825, location V) . This shall
hereinafter be referred to as Plan Two. In the event the City of San Mateo does
not approve any additional exterior lighted signs, then Landlord and Tenant will
attempt to get approval for the sign substitution as hereinafter described. This
shall hereinafter be described as Plan Three.

a. Plan One In this case Landlord and Tenant shall
jointly and co-operatively apply to the City of San Mateo for approval to place
two exterior building-mounted lighted signs on Building One (1825, locations V
& VI). In the event the City of San Mateo approves this plan, then Landlord
shall grant Tenant the right to place two exterior building- mounted lighted
signs, one on Building One (1825) and one on Building Two (1875). One of
Tenant's additional signs shall be east-facing (in locations V or III) and one
of Tenant's additional signs shall be west-facing (in locations VI or IV).
Landlord's exterior building-mounted lighted signs shall be in the reciprocal
locations from Tenant's signs and shall require the relocation of one of
Landlord's two existing signs. The following table outlines the
alternatives:



|TENANT SIGN LOCATION | LANDLORD SIGN LOCATION
|-------------------- | ----------------------
|III & VI             | V & IV                
|V & IV               | III & VI              



It shall be at Tenant's preference which of the above
alternatives is implemented. In addition, at such time as Tenant places Tenant's
signs on Buildings One (1825) and Two (1875), Tenant agrees to remove Tenant's
west-facing sign on Building Three (1855, location II) . Tenant shall pay all
costs associated with this sign removal including the cost to repair any damage
to the Premises and any costs to repaint the area of the building from which the
sign was removed so as to render the area uniform in appearance.

b. Plan Two In the event The City of San Mateo denies
approval for two additional exterior building-mounted lighted signs for Building
One, then Landlord and Tenant shall apply for approval to place one additional
exterior building-mounted lighted sign on Building One (1825, location V). In
the event the City of San Mateo approves Plan Two, Landlord hereby grants Tenant
the right to place one additional exterior-mounted lighted sign on either
Building One (1825, location V) or Building Two (1875, location III) . The
selection of Tenant's additional sign location shall be at Tenant's preference.
In the event Tenant selects location III, Landlord, at landlord's expense, shall
relocate Landlord's existing sign in location III to location V, and Tenant's
additional sign shall be in location III. In the event Tenant selects location
V, Landlord's sign shall remain in location III. Under this Plan Two, Tenant's
existing signs on Building Three (1855, locations I and II), and Landlord's
existing sign on Building Two (1875, location IV), shall remain in place.

c. Plan Three In the event the City of San Mateo denies both Plan One and Plan Two, Landlord hereby grants Tenant the right to replace
Landlord's existing sign on Building Two (1875, location IV) with Tenant's sign.
In this event Landlord's other sign on Building Two (1875, location III) and
Tenant's signs on Building Three (1855, locations I & II) shall remain in
place.

10. LEASE IN FULL FORCE AND EFFECT

Except as herein and modified the Lease shall remain in full
force and effect.

IN WITNESS WHEREOF, the parties have signed this Eleventh
Amendment of Lease, which for reference purposes shall be deemed to have been
dated as the date above written.

|LANDLORD:                                        | TENANT:                                                
|------------------------------------------------ | -------------------------------------------------------
|CROSSROADS ASSOCIATES, and
CLOCKTOWER ASSOCIATES | SIEBEL SYSTEMS, Inc., a
        Delaware Corporation   
|/s/ Boyd Smith
	Title Partner                    | /s/ Jeffrey T. Amann
      TitleDirector, Legal Affairs

---

THIRTEENTH AMENDMENT OF LEASE



This Thirteenth Amendment of Lease is made and entered into
this 7th day of December, 1999, by and between Crossroads Associates and
Clocktower Associates (Landlord), and Siebel Systems, Inc. a Delaware
Corporation (Tenant).



RECITALS

A.WHEREAS, Landlord and Tenant entered into a Lease
dated June 4th, 1996, (the Lease) for the lease of approximately 66,426 gross
square feet of space located in the five story Building located at 1855 South
Grant Street, San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenant's option to lease the fourth floor of the Building located at 1875 South
Grant Street, San Mateo, San Mateo County, California (and hereinafter referred
to as the 1875 Building) and by letter dated December 17th, 1996, Tenant
exercised Tenant's option to lease the tenth floor of the 1875 Building; and

C. WHEREAS, by First Amendment of Lease dated March 17, 1997
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of the 1875
Building, commencing April 1st, 1997, contingent upon Landlord obtaining a lease
termination agreement with California Federal Bank, which lease termination
agreement was not obtained thereby rendering the First Amendment of Lease void;
and

D. WHEREAS, by Second Amendment of Lease dated March 19, 1997
Tenant leased an additional 12,926 gross square feet of space located on the
first floor of the 1875 Building; and

E. WHEREAS, by letter dated May 23, 1997, Tenant exercised
Tenant's Option to lease the ninth floor of the 1875 Building, and by letter
dated July 28th, 1997 Tenant exercised Tenant's Option to lease the Eighth floor
of the 1875 Building, thereby bringing Tenant's total leased area (subject to
the Ninth floor becoming available) to 150,160 gross square feet of space;
and

F. WHEREAS, by Third Amendment of Lease dated September 1st,
1997 Landlord and Tenant agreed to an early commencement of lease for Suite 130,
in the 1875 Building, such that the Suite 130 Lease commenced September 1st,
1997.

G. WHEREAS, by Fourth Amendment of Lease dated April 2nd, 1998,
Landlord and Tenant agreed that Landlord will allow Tenant to make certain
improvements to Tenant's Premises in the 1875 Building and Tenant further agreed
to additional compensation for additional parking.

H. WHEREAS, Bay Networks exercised its option to extend its
lease on the ninth floor of the 1875 Building, thereby making Tenant's exercise
of option to lease the ninth floor void and therefore bringing Tenant's total
leased area to 132,458 square feet.

I. WHEREAS, by Fifth Amendment of Lease dated May 8, 1998, in
the 1875 Building, Tenant leased an additional 9,453 square feet on the second
floor and 6,973 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 148,884 square feet.

J. WHEREAS, by Sixth Amendment of Lease dated September 16,
1998, in the 1875 Building, Tenant leased an additional 7,113 square feet on the
fifth floor (which includes Tenant's proportionate share of building common
areas) and which space was further identified as Suite 500, thereby bringing
Tenant's total leased area to 155,997 square feet.

K. WHEREAS, by Seventh Amendment of Lease dated December 1,
1998, Tenant agreed to lease Suite 500 prior to March 1, 1999 in the event it
became available and Tenant's lease of Suite 500 commenced December 29,
1998.

L. WHEREAS, by Eighth Amendment of Lease dated January 15, 1999
in the 1875 Building, Tenant leased an additional 810 square feet on the second
floor and 4,288 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 161,095 square feet.

M. WHEREAS, by Ninth Amendment of Lease dated January 25, 1999
in the 1875 Building, Tenant leased an additional 5,221 square feet on the sixth
floor and 2,695 square feet on the seventh floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 169,011 square feet.

N. WHEREAS, by Tenth Amendment of Lease dated February 25, 1999
in the 1875 Building, Tenant leased an additional 4,319 square feet on the
second floor (which includes Tenant's proportionate share of building common
areas), thereby bringing Tenant's total leased area to 173,330 square feet.

0. WHEREAS, by Eleventh Amendment of Lease dated April 7,
1999 in the 1825 Building, Tenant leased an additional 7,509 square feet on the
first floor, 11,417 square feet on the fifth floor, 17,702 on the eighth floor
and 17,702 square feet on the ninth floor (which includes Tenant's proportionate
share of building common areas), thereby bringing Tenant's total leased area to
227,660 square feet.

P. WHEREAS, by Twelfth Amendment of Lease dated May 26, 1999
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
1,657 of rentable square feet of space located on the third floor of the 1875
Building, effective July 1st, 1999, contingent upon Landlord obtaining a lease
termination agreement with PRS International, which lease termination agreement
was not obtained thereby rendering the Twelfth Amendment of Lease void; and

Q. WHEREAS, in the 1875 Building, Tenant now desires to lease
and additional 2,552 square feet on the second floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 230,212 square feet.

NOW, THEREFORE, in consideration of the foregoing and other
good and valuable consideration, receipt of which is hereby acknowledged,
Landlord and Tenant agree as follows:

1. The area to be leased hereunder shall hereinafter be
referred to as "Suite 210" and is described as follows: 2,552 gross square feet
of space, which includes Tenant's prorata share of Building common areas,
located on the second floor of the Building located at 1875 South Grant Street,
San Mateo, San Mateo County, California and as further outlined in red on
Exhibit "A".

Tenant hereby acknowledges that Suite 210 is currently leased
to Websense. Tenant's Lease of Suite 210 is contingent upon Landlord entering
into, in Landlord's sole opinion, an acceptable Lease Termination Agreement with
Websense. In the event Landlord does not enter into such a lease termination
agreement then this Thirteenth Amendment of Lease shall be void and of no force
and effect between the parties and neither Landlord nor Tenant shall be liable
to one another for having entered into this Thirteenth Amendment of Lease and
the Lease shall remain in full force and effect.

2. EFFECTIVE DATE

Subject to Paragraph 1 above, the Effective Date for Suite 210 shall be January 1, 2000.

3. TERM

Subject to Paragraph 1 above, commencing upon the Effective
Date Landlord agrees to lease to Tenant and Tenant agrees to lease and hire from
Landlord Suite 210.

The Term of Lease for Suite 210 shall terminate August 31,
2008. Landlord and Tenant each acknowledge that the expiration date of the term
of Lease for Suite 210 is different from the expiration date of the term of
lease for other space leased by Tenant, including the expiration date of the
term of lease for the 1855 Building and the "Core Space" (as defined in
Paragraph 3 of the Fifth Amendment of Lease). In the event the term of Tenant's
lease for the Core Space expires and Tenant vacates the Core Space,
nevertheless, the term of lease for Suite 210 leased hereunder shall expire
August 31st, 2008 and all the terms and conditions of the Lease shall remain in
full force and effect and shall pertain to the space leased under this
Thirteenth Amendment of Lease. Furthermore, it is hereby agreed that the Lease
for Suite 210 shall be subject to the Option to Extend granted to Tenant per
paragraph 48 of the Lease such that in the event that Tenant exercises its
option to extend the Lease on the Core Space such that the Lease for the Core
Space is extended to July 31st, 2011, then the Lease for Suite 210 shall
automatically be extended from August 31, 2008 to July 31st, 2011. The Basic and
Additional Rent on Suite 210 for the period September 1st, 2008 to July 31st,
2011 (provided Tenant has exercised its option per paragraph 48 of the Lease)
shall be at the same rate as Tenant is then paying on the Core Space. As is
stated in Paragraph 48 (f), Tenant's second Option to Extend shall apply to all
space then leased by Tenant as of the date of the exercise of the second
option.

4. BASIC RENT

Commencing upon the Effective Date, Tenant's monthly Basic Rent
for Suite 210 shall be 2,552 s.f. x $3.40 = $8,676.80 per month. This amount
shall be adjusted August 8th, 2000 and annually thereafter, in the same manner
and upon the same date and with the same limitations as described in Paragraph
38 of the Lease.

Notwithstanding anything herein to the contrary, for Suite 210,
Landlord hereby grants Tenant two months Basic Rent abatement on such suite.
Such Basic Rent Abatement shall be granted to Tenant irrespective whether Tenant
occupies the Premises or not during the two month period immediately following
the Effective Date. For example, the Effective Date for Suite 210 is January
1st, 2000, Tenant's lease on Suite 210 will commence January 1st, 2000, and the
Basic Rent described above for Suite 210 will commence March 1st, 2000.

5. ADDITIONAL RENT

Commencing upon the Effective Date, Tenant's Additional Rent as
described in Paragraph 4D of the Lease shall be the then current rate being
charged to tenants occupying Building 1875 and shall continue to be adjusted per
the terms and conditions of Paragraph 4D.

6. AS-IS

Tenant agrees to lease suite 210 hereunder in an "as- is"
condition, and any alteration or modification to the Premises shall be made in
accordance with paragraphs 8 & 9 of the Lease at Tenant's sole cost and
expense and shall not delay the commencement of Lease for Suite 210 nor delay
the payment of rent.

7. PARKING

Upon the Effective Date for Suite 210, Tenant's total parking
allocation shall be increased by 8 spaces.

8. NO BROKERS

Landlord and Tenant mutually acknowledge that neither Landlord
nor Tenant have had any dealings with any real estate brokers or agents in
connection with the negotiation of this Thirteenth Amendment of Lease which has
resulted in any obligation to pay a leasing commission.

9. LEASE IN FULL FORCE AND EFFECT

Except as herein and modified the Lease shall remain in full
force and effect.

IN WITNESS WHEREOF, the parties have signed this Thirteenth
Amendment of Lease, which for reference purposes shall be deemed to have been
dated as the date above written.

|LANDLORD:                     | TENANT:                                                
|----------------------------- | -------------------------------------------------------
|CROSSROADS ASSOCIATES         | SIEBEL SYSTEMS, Inc., a
        Delaware Corporation   
|/s/ Boyd Smith
	Title Partner | /s/ Jeffrey T. Amann
      TitleDirector, Legal Affairs

CLOCKTOWER ASSOCIATES

/s/ Boyd Smith
Title Partner

---

FOURTEENTH AMENDNENT OF LEASE



This Fourteenth Amendment of Lease is made and entered into
this 17th day of December, 1999, by and between Crossroads Associates and
Clocktower Associates (Landlord),and Siebel Systems, Inc. a Delaware
Corporation (Tenant).

RECITALS

A.WHEREAS, Landlord and Tenant entered into a Lease
dated June 4th, 1996, (the Lease) for the lease of approximately 66,426 gross
square feet of space located in the five story Building located at 1855 South
Grant Street, San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenant's option to lease the fourth floor of the Building located at 1875 South
Grant Street, San Mateo, San Mateo County, California (and hereinafter referred
to as the 1875 Building) and by letter dated December 17th, 1996, Tenant
exercised Tenant's option to lease the tenth floor of the 1875 Building; and

C. WHEREAS, by First Amendment of Lease dated March 17, 1997
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of the 1875
Building, commencing April 1st, 1997, contingent upon Landlord obtaining a lease
termination agreement with California Federal Bank, which lease termination
agreement was not obtained thereby rendering the First Amendment of Lease void;
and

D. WHEREAS, by Second Amendment of Lease dated March 19, 1997
Tenant leased an additional 12,926 gross square feet of space located on the
first floor of the 1875 Building; and

E. WHEREAS, by letter dated May 23, 1997, Tenant exercised
Tenant's Option to lease the ninth floor of the 1875 Building, and by letter
dated July 28th, 1997 Tenant exercised Tenant's Option to lease the Eighth floor
of the 1875 Building, thereby bringing Tenant's total leased area (subject to
the Ninth floor becoming available) to 150,160 gross square feet of space;
and

F. WHEREAS, by Third Amendment of Lease dated September 1st,
1997 Landlord and Tenant agreed to an early commencement of lease for Suite 130,
in the 1875 Building, such that the Suite 130 Lease commenced September 1st,
1997; and

G. WHEREAS, by Fourth Amendment of Lease dated April 2nd, 1998,
Landlord and Tenant agreed that Landlord will allow Tenant to make certain
improvements to Tenant's Premises in the 1875 Building and Tenant further agreed
to additional compensation for additional parking; and

H. WHEREAS, Bay Networks exercised its option to extend its
lease on the ninth floor of the 1875 Building, thereby making Tenant's exercise
of option to lease the ninth floor void and therefore bringing Tenant's total
leased area to 132,458 square feet; and

I. WHEREAS, by Fifth Amendment of Lease dated May 8, 1998, in
the 1875 Building, Tenant leased an additional 9,453 square feet on the second
floor and 6,973 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 148,884 square feet; and

J. WHEREAS, by Sixth Amendment of Lease dated September 16,
1998, in the 1875 Building, Tenant leased an additional 7,113 square feet on the
fifth floor (which includes Tenant's proportionate share of building common
areas) and which space was further identified as Suite 500, thereby bringing
Tenant's total leased area to 155,997 square feet; and

K. WHEREAS, by Seventh Amendment of Lease dated December 1,
1998, Tenant agreed to lease Suite 500 prior to March 1, 1999 in the event it
became available and Tenant's lease of Suite 500 commenced December 29, 1998;
and

L. WHEREAS, by Eighth Amendment of Lease dated January 15, 1999
in the 1875 Building, Tenant leased an additional 810 square feet on the second
floor and 4,288 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 161,095 square feet; and

M. WHEREAS, by Ninth Amendment of Lease dated January 25, 1999
in the 1875 Building, Tenant leased an additional 5,221 square feet on the sixth
floor and 2,695 square feet on the seventh floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 169,011 square feet; and

N. WHEREAS, by Tenth Amendment of Lease dated February 25, 1999
in the 1875 Building, Tenant leased an additional 4,319 square feet on the
second floor (which includes Tenant's proportionate share of building common
areas), thereby bringing Tenant's total leased area to 173,330 square feet;
and

O. WHEREAS, by Eleventh Amendment of Lease dated April 7, 1999
in the 1825 Building, Tenant leased an additional 7,509 square feet on the first
floor, 11,417 square feet on the fifth floor, 17,702 on the eighth floor and
17,702 square feet on the ninth floor (which includes Tenant's proportionate
share of building common areas), thereby bringing Tenant's total leased area to
227,660 square feet; and

P. WHEREAS, by Twelfth Amendment of Lease dated May 26, 1999
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
1,657 of rentable square feet of space located on the third floor of the 1875
Building, effective July 1st, 1999, contingent upon Landlord obtaining a lease
termination agreement with PRS International, which lease termination agreement
was not obtained thereby rendering the Twelfth Amendment of Lease void; and

Q. WHEREAS, by Thirteenth Amendment of Lease dated December 7,
1999, Tenant leased an additional 2,552 square feet on the second floor (which
includes Tenant's proportionate share of building common areas) of the 1875
Building, thereby bringing Tenant's total leased area to 230,212 square feet;
and

R. WHEREAS, in the 1875 Building, Tenant now desires to lease
an additional 1,608 square feet on the fifth floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 231,820 square feet.

NOW, THEREFORE, in consideration of the foregoing and other
good and valuable consideration, receipt of which is hereby acknowledged,
Landlord and Tenant agree as follows:

1. The area to be leased hereunder shall hereinafter be
referred to as "Suite 540" and is described as follows: 1,608 rentable square
feet of space, which includes Tenant's prorata share of Building common areas,
located on the fifth floor of the Building located at 1875 South Grant Street,
San Mateo, San Mateo County, California and as further outlined in red on
Exhibit "A".

2. EFFECTIVE DATE

The "Effective Date" for the commencement of Lease for Suite
540 shall hereinafter be defined as April 1, 2000.

3. TERM

The term of Lease for Suite 540 shall commence upon the
Effective Date and shall terminate August 31st, 2008. Landlord and Tenant each
acknowledge that the expiration date of the term of Lease for Suite 540 is
different from the expiration date of the term of lease for the 1855 Building
and The "Core Space" (as defined in Paragraph 3 of the Fifth Amendment of
Lease). In the event the term of Tenant's lease for the Core Space expires and
Tenant vacates the Core Space, nevertheless,

the term of lease for Suite 540 leased hereunder shall expire
August 31st, 2008 and all the terms and conditions of the Lease shall remain in
full force and effect and shall pertain to the space leased under this
Fourteenth Amendment of Lease. Furthermore, it is hereby agreed that the Lease
for Suite 540 shall be subject to the Option to Extend granted to Tenant per
paragraph 48 of the Lease. In the event that Tenant exercises its option to
extend the Lease on the Core Space such that the Lease for the Core Space is
extended to July 31st, 2011, then the Lease for Suite 540 shall automatically be
extended from August 31st, 2008 to July 31st, 2011. The Basic and Additional
Rent on Suite 540 for the period September 1st, 2008 to July 31st, 2011
(provided Tenant has exercised its option per paragraph 48 of the Lease) shall
be at the same rate as Tenant is then paying on the Core Space. As is stated in
Paragraph 48 (f), Tenant's second Option to Extend shall apply to all space then
leased by Tenant as of the date of the exercise of the second option.

4. BASIC RENT

Commencing upon the Effective Date, Tenant's monthly Basic Rent
for Suite 540 shall be 1,608 s.f. x $3.40 = $5,467.20 per month. This amount
shall be adjusted August 8th, 2000 and annually thereafter, in the same manner
and upon the same date and with the same limitations as described in Paragraph
38 of the Lease.

Notwithstanding anything herein to the contrary, for Suite 540,
Landlord hereby grants Tenant two months Basic Rent abatement on such suite.
Such Basic Rent Abatement shall be granted to Tenant irrespective whether Tenant
occupies the Premises or not during the two month period immediately following
the Effective Date. For example, the Effective Date for Suite 540 is April 1st,
2000, Tenant's lease on Suite 540 will commence April 1st, 2000, and the Basic
Rent described above for Suite 540 will commence June 1st, 2000.

5. ADDITIONAL RENT

Commencing upon the Effective Date, Tenant's Additional Rent as
described in Paragraph 4D of the Lease shall be the then current rate being
charged to tenants occupying Building 1875 and shall continue to be adjusted per
the terms and conditions of Paragraph 4D.

6. AS-IS

Tenant agrees to lease suite 540 hereunder in an "as-is"
condition, and any alteration or modification to the Premises shall be made in
accordance with paragraphs 8 & 9 of the Lease at Tenant's sole cost and
expense and shall not delay the commencement of Lease for Suite 540 nor delay
the payment of rent.

7. PARKING

Upon the Effective Date for Suite 540, Tenant's total parking
allocation shall be increased by 5 spaces.

8. NO BROKERS

Landlord and Tenant mutually acknowledge that neither Landlord
nor Tenant have had any dealings with any real estate brokers or agents in
connection with the negotiation of this Fourteenth Amendment of Lease which has
resulted in any obligation to pay a leasing commission.

9. LEASE IN FULL FORCE AND EFFECT

Except as herein and modified the Lease shall remain in full
force and effect.



IN WITNESS WHEREOF, the parties have signed this Fourteenth
Amendment of tease, which for reference purposes shall be deemed to have been
dated as the date above written.

|LANDLORD:                        | TENANT:                                                
|-------------------------------- | -------------------------------------------------------
|CROSSROADS ASSOCIATES            | SIEBEL SYSTEMS, Inc., a
        Delaware Corporation   
|/s/ Dick Jacobson
	Title Partner | /s/ Jeffrey T. Amann
      TitleDirector, Legal Affairs

CLOCKTOWER ASSOCIATES

/s/ Dick Jacobson
Title Partner

---

FIFTEENTH AMENDMENT OF LEASE

This Fifteenth Amendment of Lease is made and entered into this
12th day of January, 2000, by and between Crossroads Associates and Clocktower
Associates (Landlord), and Siebel Systems, Inc. a Delaware Corporation
(Tenant).



RECITALS

A.WHEREAS, Landlord and Tenant entered into a Lease
dated June 4th, 1996, (the Lease) for the lease of approximately 66,426 gross
square feet of space located in the five story Building located at 1855 South
Grant Street, San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenant's option to lease the fourth floor of the Building located at 1815 South
Grant Street, San Mateo, San Mateo County, California (and hereinafter referred
to as the 1875 Building) and by letter dated December 17th, 1996, Tenant
exercised Tenant's option to lease the tenth floor of the 1875 Building; and

C. WHEREAS, by First Amendment of Lease dated March 17, 1997
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of the 1875
Building, commencing April 1st, 1997, contingent upon Landlord obtaining a lease
termination agreement with California Federal Bank, which lease termination
agreement was not obtained thereby rendering the First Amendment of Lease void;
and

D. WHEREAS, by Second Amendment of Lease dated March 19, 1997
Tenant leased an additional 12,926 gross square feet of space located on the
first floor of the 1875 Building; and

E. WHEREAS, by letter dated May 23, 1997, Tenant exercised
Tenant's Option to lease the ninth floor of the 1875 Building, and by letter
dated July 28th, 1997 Tenant exercised Tenant's Option to lease the Eighth floor
of the 1875 Building, thereby bringing Tenant's total leased area (subject to
the Ninth floor becoming available) to 150,160 gross square feet of space;
and

F. WHEREAS, by Third Amendment of Lease dated September 1st,
1997 Landlord and Tenant agreed to an early commencement of lease for Suite 130,
in the 1875 Building, such that the Suite 130 Lease commenced September 1st,
1997; and

G. WHEREAS, by Fourth Amendment of Lease dated April 2nd, 1998,
Landlord and Tenant agreed that Landlord will allow Tenant to make certain
improvements to Tenant's Premises in the 1875 Building and Tenant further agreed
to additional compensation for additional parking; and

H. WHEREAS, Bay Networks exercised its option to extend its
lease on the ninth floor of the 1875 Building, thereby making Tenant's exercise
of option to lease the ninth floor void and therefore bringing Tenant's total
leased area to 132,458 square feet; and

I. WHEREAS, by Fifth Amendment of Lease dated May 8, 1998, in
the 1875 Building, Tenant leased an additional 9,453 square feet on the second
floor and 6,973 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 148,884 square feet; and

J. WHEREAS, by Sixth Amendment of Lease dated September 16,
1998, in the 1875 Building, Tenant leased an additional 7,113 square feet on the
fifth floor (which includes Tenant's proportionate share of building common
areas) and which space was further identified as Suite 500, thereby bringing
Tenant's total leased area to 155,997 square feet; and

K. WHEREAS, by Seventh Amendment of Lease dated December 1,
1998, Tenant agreed to lease Suite 500 prior to March 1, 1999 in the event it
became available and Tenant's lease of Suite 500 commenced December 29, 1998;
and

L. WHEREAS, by Eighth Amendment of Lease dated January 15, 1999
in the 1875 Building, Tenant leased an additional 810 square feet on the second
floor and 4,288 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 161,095 square feet; and

M. WHEREAS, by Ninth Amendment of Lease dated January 25, 1999
in the 1875 Building, Tenant leased an additional 5,221 square feet on the sixth
floor and 2,695 square feet on the seventh floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 169,011 square feet; and

N. WHEREAS, by Tenth Amendment of Lease dated February 25, 1999
in the 1875 Building, Tenant leased an additional 4,319 square feet on the
second floor (which includes Tenant's proportionate share of building common
areas), thereby bringing Tenant's total leased area to 173,330 square feet
and

O. WHEREAS, by Eleventh Amendment of Lease dated April 7,1999
in the 1825 Building, Tenant leased an additional 7,509 square feet on the first
floor, 11,417 square feet on the fifth floor, 17,702 on the eighth floor and
17,702 square feet on the ninth floor (which includes Tenant's proportionate
share of building common areas), thereby bringing Tenant's total leased area to
227,660 square feet; and

P. WHEREAS, by Twelfth Amendment of Lease dated May 26, 1999
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
1,657 of rentable square feet of space located on the third floor of the 1875
Building, effective July 1st, 1999, contingent upon Landlord obtaining a lease
termination agreement with PRS International, which lease termination agreement
was not obtained thereby rendering the Twelfth Amendment of Lease void; and

Q. WHEREAS, by Thirteenth Amendment of Lease dated December 7,
1999, Tenant leased an additional 2,552 square feet on the second floor (which
includes Tenant's proportionate share of building common areas) of the 1875
Building, thereby bringing Tenant's total leased area to 230,212 square feet;
and

R. WHEREAS, by the still to be executed Fourteenth Amendment of
Lease dated December 7, 1999, Tenant intends to lease an additional 1,608 square
feet on the fifth floor (which includes Tenant's proportionate share of building
common areas) of the 1875 Building, which upon execution of the Fourteenth
Amendment of Lease shall thereby bringing Tenant's total leased area to 231,820
square feet; and

S. WHEREAS, in the 1875 Building, Tenant now desires to lease
an additional 1,657 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 233,477 square feet.

NOW, THEREFORE, in consideration of the foregoing and other
good and valuable consideration, receipt of which is hereby acknowledged,
Landlord and Tenant agree as follows:



1. The areas to be leased hereunder are all located in the
Building located at 1875 South Grant Street, San Mateo, San Mateo County,
California and are further described as follows:



a) Suite 31D-D,E (PRS International)

Comprising 1,027 gross square feet of space, including Tenant's
prorata share of Building common areas, located on the third floor and as
further described in red on Exhibit "Al".



b) Suite 310-C (Bowman Capital Management)

Comprising 630 gross square feet of space, which includes
Tenant's prorata share of Building common areas, located on the third floor and
as further outlined in red on Exhibit "A2".

Tenant hereby acknowledges that the two suites to be leased
hereunder, Suites 310-D,E and 310-C are currently leased to PRS International,
Inc. and Bowman Capital Management respectively. Tenant's Lease of Suite 310-D,E
is contingent upon Landlord entering into, in Landlord's sole opinion, an
acceptable lease termination agreement with PRS International for the referenced
suite. In the event Landlord and PRS International do not enter into such a
lease termination agreement, then the provisions of this Fifteenth Amendment of
Lease shall be void and of no force and effect between the parties, neither
Landlord nor Tenant shall be liable to one another for having entered into this
Fifteenth Amendment of Lease, and all other terms and conditions of the Lease
shall remain in full force and effect. Landlord's Lease Agreement with Bowman
Capital Management is on a month-to-month basis, and at such time that both an
acceptable lease termination agreement is executed by PRS International, and
Landlord has received a fully executed copy of this Fifteenth Amendment of
Lease, Landlord will provide written notification to Bowman Capital, terminating
their lease on February 29, 2000.

2. EFFECTIVE DATE

Subject to Paragraph 1 above, the Effective Dates shall be as
follows:

(a) Suite 310-D,E - March 1, 2000
(b) Suite 310-C - March 1, 2000

3. TERM

Subject to Paragraph 1 above, commencing upon the respective
Effective Dates Landlord agrees to lease to Tenant and Tenant agrees to lease
and hire from Landlord Suites 310-D,E and 310-C. The Term of Lease for Suites
310-D,E and 310-C shall terminate August 31, 2008. Landlord and Tenant each
acknowledge that the expiration date of the term of Lease for Suites 3l0-D,E and
310-C is different from the expiration date of the term of lease for other space
leased by Tenant, including the expiration date of the term of lease for the
1855 Building and the "Core Space" (as defined in Paragraph 3 of the Fifth
Amendment of Lease). In the event the term of Tenant's lease for the Core Space
expires and Tenant vacates the Core Space, nevertheless, the term of lease for
Suites 310-D,E and 310-C leased hereunder shall expire August 31st, 2008 and all
the terms and conditions of the Lease shall remain in full force and effect and
shall pertain to the space leased under this Fifteenth Amendment of Lease.
Furthermore, it is hereby agreed that the Lease for Suites 3l0-D,E and 310-C
shall be subject to the Option to Extend granted to Tenant per paragraph 48 of
the Lease such that in the event that Tenant exercises its option to extend the
Lease on the Core Space such that the Lease for the Core Space is extended to
July 31st, 2011, then the Lease for Suites 310-D,E and 310-C shall automatically
be extended from August 31, 2008 to July 31st, 2011. The Basic and Additional
Rent on Suites 310-D,E and 310-C for the period September 1st, 2008 to July
31st, 2011 (provided Tenant has exercised its option per paragraph 48 of the
Lease) shall be at the same rate as Tenant is then paying on the Core Space. As
is stated in Paragraph 48(f), Tenant's second Option to Extend shall apply to
all space then leased by Tenant as of the date of the exercise of the second
option.

4. BASIC RENT

The Basic Rent for the additional space leased per this
Fifteenth Amendment, commencing upon the Effective Date, shall be $3.40 per
square foot per month multiplied by the square footage leased, as follows:





|            
|------------
|Suite       
|            
|310-D,E310-C

The Basic Rent described above shall be adjusted August 8th,
2000 and annually thereafter, in the same manner and upon the same date and with
the same limitations as described in paragraph 38 of the Lease.



Notwithstanding anything herein to the contrary, for Suites
310-D,E and 310-C, Landlord hereby grants Tenant two months Basic Rent abatement
for each suite. Such Basic Rent Abatement shall be granted to Tenant
irrespective of whether Tenant occupies the Premises or not during the two-month
period immediately following the Effective Date. For example, if the Effective
Date for Suites 310-D,E and 310-C is March 1, 2000, Tenant's lease on Suites
310-D,E and 310-C will commence March 1, 2000, and the Basic Rent described
above for Suites 310-D,E and 310-C will commence May 1, 2000, irrespective of
Tenant's occupancy.

5. ADDITIONAL RENT

Commencing upon the Effective Date, Tenants Additional Rent for
each suite, as described in Paragraph 4D of the Lease, shall be the then current
rate per square foot per month being charged to tenants occupying Building 1875
multiplied by the respective square footages and shall continue to be adjusted
per the terms and conditions of Paragraph 4D.

6. AS-IS

Tenant agrees to lease each suite hereunder in an "as-is"
condition, and any alteration or modification to the Premises shall be made in
accordance with paragraphs 8 & 9 of the Lease at Tenant's sole cost and
expense and shall not delay the commencement of Lease for each of the Suites nor
delay the payment of rent.

7. PARKING

On the Effective Date, Tenant's total parking allocation shall
be increased as follows:





|Suite 310-D,E |  | 3 spaces
|------------- |  | --------
|Suite 310-C   |  | 2 spaces

8. NO BROKERS

Landlord and Tenant mutually acknowledge that neither Landlord
nor Tenant have had any dealings with any real estate brokers or agents in
connection with the negotiation of this Fifteenth Amendment of Lease which has
resulted in any obligation to pay a leasing commission.

10. LEASE IN FULL FORCE AND EFFECT

Except as herein and modified the Lease shall remain in full
force and effect.

IN WITNESS WHEREOF, the parties have signed this Fifteen
Amendment of Lease, which for reference purposes shall be deemed to have been
dated as the date above written.

|LANDLORD:                        | TENANT:                                                
|-------------------------------- | -------------------------------------------------------
|CROSSROADS ASSOCIATES            | SIEBEL SYSTEMS, Inc., a
        Delaware Corporation   
|/s/ Dick Jacobson
	Title Partner | /s/ Jeffrey T. Amann
      TitleDirector, Legal Affairs

CLOCKTOWER ASSOCIATES

/s/ Dick Jacobson
Title Partner

---

SIXTEENTH AMENDMENT OF LEASE

This Sixteenth Amendment of Lease is made and entered into this
12th day of September, 2000, by and between Crossroads Associates and Clocktower
Associates (Landlord), and Siebel Systems, Inc. a Delaware Corporation
(Tenant).

RECITALS

A. WHEREAS, Landlord and Tenant entered into a Lease dated June
4th, 1996, (the Lease) for the lease of approximately 66,426 gross square feet
of space located in the five story Building located at 1855 South Grant Street,
San Mateo, San Mateo County, California; and

B. WHEREAS, by letter dated October 30th, 1996 Tenant exercised
Tenant's option to lease the fourth floor of the Building located at 1875 South
Grant Street, San Mateo, San Mateo County, California (and hereinafter referred
to as the 1875 Building) and by letter dated December 17th, 1996, Tenant
exercised Tenant's option to lease the tenth floor of the 1875 Building; and

C. WHEREAS, by First Amendment of Lease dated March 17, 1997
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
12,926 rentable square feet of space located on the first floor of the 1875
Building, commencing April 1st, 1997, contingent upon Landlord obtaining a lease
termination agreement with California Federal Bank, which lease termination
agreement was not obtained thereby rendering the First Amendment of Lease void;
and

D. WHEREAS, by Second Amendment of Lease dated March 19, 1997
Tenant leased an additional 12,926 gross square feet of space located on the
first floor of the 1875 Building; and

E. WHEREAS, by letter dated May 23, 1997, Tenant exercised
Tenant's Option to lease the ninth floor of the 1875 Building, and by letter
dated July 28th, 1997 Tenant exercised Tenant's Option to lease the Eighth floor
of the 1875 Building, thereby bringing Tenant's total leased area (subject to
the Ninth floor becoming available) to 150,160 gross square feet of space;
and

F. WHEREAS, by Third Amendment of Lease dated September 1st,
1997 Landlord and Tenant agreed to an early commencement of lease for Suite 130,
in the 1875 Building, such that the Suite 130 Lease commenced September 1st,
1997; and

G. WHEREAS, by Fourth Amendment of Lease dated April 2nd, 1998,
Landlord and Tenant agreed that Landlord will allow Tenant to make certain
improvements to Tenant's Premises in the 1875 Building and Tenant further agreed
to additional compensation for additional parking; and

H. WHEREAS, Bay Networks exercised its option to extend its
lease on the ninth floor of the 1875 Building, thereby making Tenant's exercise
of option to lease the ninth floor void and therefore bringing Tenant's total
leased area to 132,458 square feet; and

I. WHEREAS, by Fifth Amendment of Lease dated May 8, 1998, in
the 1875 Building, Tenant leased an additional 9,453 square feet on the second
floor and 6,973 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 148,884 square feet; and

J. WHEREAS, by Sixth Amendment of Lease dated September 16,
1998, in the 1875 Building, Tenant leased an additional 7,113 square feet on the
fifth floor (which includes Tenant's proportionate share of building common
areas) and which space was further identified as Suite 500, thereby bringing
Tenant's total leased area to 155,997 square feet; and

K. WHEREAS, by Seventh Amendment of Lease dated December 1,
1998, Tenant agreed to lease Suite 500 prior to March 1, 1999 in the event it
became available and Tenant's lease of Suite 500 commenced December 29, 1998;
and

L. WHEREAS, by Eighth Amendment of Lease dated January 15, 1999
in the 1875 Building, Tenant leased an additional 810 square feet on the second
floor and 4,288 square feet on the third floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 161,095 square feet; and

M. WHEREAS, by Ninth Amendment of Lease dated January 25, 1999
in the 1875 Building, Tenant leased an additional 5,221 square feet on the sixth
floor and 2,695 square feet on the seventh floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 169,011 square feet; and

N. WHEREAS, by Tenth Amendment of Lease dated February 25, 1999
in the 1875 Building, Tenant leased an additional 4,319 square feet on the
second floor (which includes Tenant's proportionate share of building common
areas), thereby bringing Tenant's total leased area to 173,330 square feet;
and

O. WHEREAS, by Eleventh Amendment of Lease dated April 7, 1999
in the 1825 Building, Tenant leased an additional 7,509 square feet on the first
floor, 11,417 square feet on the fifth floor, 17,702 on the eighth floor and
17,702 square feet on the ninth floor (which includes Tenant's proportionate
share of building common areas), thereby bringing Tenant's total leased area to
227,660 square feet; and

P. WHEREAS, by Twelfth Amendment of Lease dated May 26, 1999
Landlord agreed to lease to Tenant and Tenant agreed to lease from Landlord
1,657 of rentable square feet of space located on the third floor of the 1875
Building, effective July 1st, 1999, contingent upon Landlord obtaining a lease
termination agreement with PRS International, which lease termination agreement
was not obtained thereby rendering the Twelfth Amendment of Lease void; and

Q. WHEREAS, by Thirteenth Amendment of Lease dated December 7,
1999, Tenant leased an additional 2,552 square feet on the second floor (which
includes Tenant's proportionate share of building common areas) of the 1875
Building, thereby bringing Tenant's total leased area to 230,212 square feet;
and

R. WHEREAS, by Fourteenth Amendment of Lease dated December 7,
1999, Tenant leased an additional 1,608 square feet on the fifth floor (which
includes Tenant's proportionate share of building common areas) of the 1875
Building, thereby bringing Tenant's total leased area to 231,820 square feet;
and

S. WHEREAS, by Fifteenth Amendment of Lease dated January 12,
2000, Tenant leased an additional 1,657 square feet on the third floor (which
includes Tenant's proportionate share of building common areas) of the 1875
Building, thereby bringing Tenant's total leased area to 233,477 square feet;
and

T. WHEREAS, in the 1825 Building, Tenant now desires to lease
an additional 2,128 square feet on the second floor (which includes Tenant's
proportionate share of building common areas), thereby bringing Tenant's total
leased area to 235,605 square feet.

NOW, THEREFORE, in consideration of the foregoing and other
good and valuable consideration, receipt of which is hereby acknowledged,
Landlord and Tenant agree as follows:

1. The area to be leased hereunder shall hereinafter be
referred to as "Suite 280" and is described as follows: 2,128 rentable square
feet of space, which includes Tenant's prorate share of Building common areas,
located on the second floor of the Building located at 1825 South Grant Street,
San Mateo, San Mateo County, California and as further outlined in red on
Exhibit "A".

2. EFFECTIVE DATE

The "Effective Date" for the commencement of Lease for Suite
280 shall hereinafter be defined as October 15, 2000.

3. TERM

The Term of Lease for Suite 280 shall commence upon the
Effective Date and shall terminate April 30, 2005.

4. BASIC RENT

Commencing upon the Effective Date, Tenant's monthly Basic Rent
for Suite 280 shall be 2,128 s.f. x $7.00 = $14,896.00 per month. This amount
shall be adjusted August 8th, 2001 and annually thereafter, in the same manner
and upon the same date and with the same limitations as described in Paragraph
38 of the Lease.

Notwithstanding anything herein to the contrary, for Suite 280,
Landlord hereby grants Tenant a Basic Rent abatement in the amount of $22,700.00
(the cost for building standard carpet, base, painting, ceiling tiles and light
fixtures). Irrespective of whether Tenant occupies the Premises, such Basic Rent
Abatement shall be granted to Tenant commencing upon the Effective Date.

5. ADDITIONAL RENT

Commencing upon the Effective Date, Tenant's Additional Rent
for Suite 280 as described in Paragraph 40 of the Lease shall be $1447.04 per
month (2128 sq.ft. x $.68 = $1447.04) and shall continue to be adjusted per the
terms and conditions of Paragraph 40.

6. AS-IS

Tenant agrees to lease suite 280 hereunder in an "as-is"
condition, and any alteration or modification to the Premises shall be made in
accordance with paragraphs 8 & 9 of the Lease at Tenant's sole cost and
expense (excepting that Landlord shall grant the Basic Rent Abatement in the
amount of $22,700 as described in paragraph 4 above) and shall not delay the
commencement of Lease for Suite 280 nor delay the payment of rent.

7. PARKING

Upon the Effective Date for Suite 280, Tenant's total parking
allocation shell be increased by 6 spaces.

8. NO BROKERS

Tenant acknowledges that Tenant shall pay all commissions due
real estate brokers or agents representing Tenant in connection with the
negotiation of this Sixteenth Amendment of Lease, and Landlord shall not be
obligated to pay any commissions to Tenant's brokers or agents.

9. LEASE IN FULL FORCE AND EFFECT

Except as herein and modified the Lease shall remain in full
force and effect.

IN WITNESS WHEREOF, the parties have signed this Sixteenth
Amendment of Lease, which for reference purposes shall be deemed to have been
dated as the date above written.



|LANDLORD:                        | TENANT:                                                       
|-------------------------------- | --------------------------------------------------------------
|CROSSROADS ASSOCIATES            | SIEBEL SYSTEMS, Inc., a
        Delaware Corporation          
|/s/ Dick Jacobson
	Title Partner | /s/ Jeffrey T. Amann
      TitleSenior Director, Legal Affairs

CLOCKTOWER ASSOCIATES

/s/ Dick Jacobson
Title Partner

---