EXHIBIT 10.34.1

Loan No. 332757

                       FIRST AMENDMENT TO PROMISSORY NOTE
                       (Mission West Properties, L.P. II)

     THIS FIRST AMENDMENT TO PROMISSORY NOTE (this "First Amendment") is made as
of the 5th day of November,  2008 between,  MISSION WEST  PROPERTIES,  L.P.II, a
Delaware limited partnership,  10050 Bandley Drive,  Cupertino, CA 95014, herein
called  "Borrower",  and THE  NORTHWESTERN  MUTUAL  LIFE  INSURANCE  COMPANY,  a
Wisconsin corporation,  720 East Wisconsin Avenue,  Milwaukee,  Wisconsin 53202,
hereinafter called "Northwestern".

                                    RECITALS

     WHEREAS, Northwestern is the owner of a certain Promissory Note executed by
MISSION WEST  PROPERTIES,  L.P. II on January 3, 2003 in the original  principal
amount of  FORTY-ONE  MILLION  THREE  HUNDRED  NINETEEN  THOUSAND  NINE  HUNDRED
SEVENTY-SIX  DOLLARS  ($41,319,976.00),  (the  "Note")  secured by,  among other
security,  i) a lien against certain property in the County of Santa Clara, City
of San Jose and the City of Milpitas,  State of California as more  particularly
described in that certain Deed of Trust and Security  Agreement (First Priority)
dated  January 3, 2003  executed by  Borrower  and  recorded  January 9, 2003 as
Document  No.  16735209  in the records of Santa Clara  County,  California,  as
amended by that certain First Amendment to Deed of Trust and Security  Agreement
(First  Priority)  and First  Amendment to Deed of Trust and Security  Agreement
(Second Priority) and First Amendment to Absolute Assignment of Leases and Rents
(Mission West  Properties,  L.P.) dated of even date herewith between Lender and
Borrower (the "First Lien  Instrument");  ii) a lien against certain property in
the  County  of Santa  Clara,  City of San  Jose,  State of  California  as more
particularly  described in that  certain  Deed of Trust and  Security  Agreement
(Second  Priority)  dated January 3, 2003  executed by Mission West  Properties,
L.P. ("MW") and recorded January 9, 2003 as Document No. 16735207 in the records
of Santa Clara County, California, as amended by that certain First Amendment to
Deed of Trust and Security  Agreement  (First  Priority) and First  Amendment to
Deed of Trust and Security  Agreement  (Second  Priority) and First Amendment to
Absolute Assignment of Leases and Rents (Mission West Properties, L.P.) dated of
even date herewith between Lender and MW (the "MW Second Lien Instrument");  and
iii) a lien against certain property in the County of Santa Clara, City of Santa
Clara and City of Cupertino, State of California, as more particularly described
in that certain Deed of Trust and Security  Agreement  and  Assignment of Leases
and Rents  (Second  Priority)  dated  January 3, 2003,  executed by Mission West
Properties, L.P. I ("MWI") and recorded January 9, 2003 as Document No. 16735208
in the records of Santa Clara  County,  California,  as amended by that  certain
First  Amendment to Deed of Trust and Security  Agreement  (First  Priority) and
First Amendment to Deed of Trust and Security  Agreement  (Second  Priority) and
First  Amendment  to  Absolute  Assignment  of Leases  and Rents  (Mission  West
Properties,  L.P.) dated of even date herewith  between Lender and MWI (the "MWI
Second Lien Instrument");

     AND WHEREAS, Northwestern has agreed to amend certain terms of the Note.

     NOW, THEREFORE,  in consideration of the above and of the mutual agreements
herein contained, the undersigned parties agree to the following:

     1. Unless  otherwise  defined  herein or otherwise  indicated,  capitalized
words and terms used but not defined  herein shall have the meaning  ascribed to
them in the Note.

     2. The  amount of the  Promissory  Note  shall be  amended  from  FORTY-ONE
MILLION  THREE  HUNDRED  NINETEEN  THOUSAND  NINE  HUNDRED  SEVENTY-SIX  DOLLARS
($41,319,976.00)  TO NINE MILLION FIVE HUNDRED  FIFTEEN  THOUSAND  EIGHT HUNDRED
SEVENTY-SEVEN DOLLARS ($9,515,877.00).

     3. The monthly  payment  amount of principal and interest  shall be amended
from $287,512.00 to $81,117.00.

     4.  Schedule 1 attached  to the Note is deleted and  replaced  with the new
Schedule 1 attached hereto.

     5. This First Amendment may be executed in two or more  counterparts,  each
of which shall be deemed an  original,  and it shall not be  necessary in making
proof of this First  Amendment  to  produce  or  account  for more than one such
counterpart.  Separate  counterparts  of this First Amendment may be executed by
the parties  hereto to the same effect as if all the  parties had  executed  the
same counterpart.

     6. Except as hereby amended the Note shall remain in full force and effect,
unchanged and in all respects, ratified and confirmed.

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<PAGE>

     7.  Nothing  herein  contained  shall  affect  the  priority  of  the  Lien
Instrument,  the MW Second Lien  Instrument  and the MWI Second Lien  Instrument
over other liens,  charges,  encumbrances or conveyances nor shall it release or
change the liability of any party who may now or hereafter be liable,  primarily
or secondarily, under or on account of the Note.

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<PAGE>



     IN  WITNESS  WHEREOF,  this  First  Amendment  has  been  executed  by  the
undersigned as of the date and year first above written.

THE NORTHWESTERN MUTUAL LIFE INSURANCE COMPANY,
                        a Wisconsin corporation

                        By:  Northwestern Investment Management Company, LLC,
                             a Delaware limited liability company, its
                             wholly-owned affiliate and authorized
                             representative

                             By:      /S/ Michael P. Cusick
                                ------------------------------------------------
                                Michael P. Cusick
                                Managing Director

                             Attest:  /S/ Donna L. Lemanczyk
                                    --------------------------------------------
                                    Donna L. Lemanczyk
                                    Assistant Secretary
(corporate seal)


                        MISSION WEST PROPERTIES, L.P.,
                        a Delaware limited partnership

                        By:  Mission West Properties, Inc.,
                             a Maryland corporation,
                             its general partner

                             By:      /S/ Raymond V. Marino
                                -----------------------------------------
                             Name:     Raymond V. Marino
                                 ----------------------------------------
                             Title:   President & COO
                                   --------------------------------------






                  (Consent of Guarantor and signature follows)

                                     - 3 -
<PAGE>




         CONSENT OF GUARANTOR:


The  undersigned  guarantor,  who is a party  under that  certain  Guarantee  of
Recourse  Obligations  dated as of June 3, 2003,  joins in the execution of this
document for the purpose of acknowledging  the above. The undersigned  guarantor
confirms that, except as herein modified,  the Guarantee of Recourse Obligations
remains in full force and effect,  unchanged  and in all  respects  ratified and
confirmed.

                                   GUARANTOR:

                                   MISSION WEST PROPERTIES, INC.,
                                   a Maryland corporation

                                   By:      /S/ Raymond V. Marino
                                      ----------------------------------------
                                   Name:    Raymond V. Marino
                                        --------------------------------------
                                   Title:   President & COO
                                         -------------------------------------


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<PAGE>




                                   SCHEDULE 1

                                Promissory Notes


Promissory Note dated January 3, 2003 executed by Mission West Properties,  L.P.
in the original  principal  amount of  $28,868,655.00,  as amended by that First
Amendment To Promissory Note dated November 5, 2008 now in the principal  amount
of $49,151,169.00.

Promissory Note dated January 3, 2003 executed by Mission West Properties,  L.P.
I in the original principal amount of  $29,811,369.00,  as amended by that First
Amendment To Promissory Note dated November 5, 2008 now in the principal  amount
of $23,228,942.00.

Promissory Note dated January 3, 2003 executed by Mission West Properties,  L.P.
II in the original principal amount of $41,319,976.00,  as amended by that First
Amendment To Promissory Note dated November 5, 2008 now in the principal  amount
of $9,551,366.00.


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