PROMISSORY NOTE


$130,000,000.00                                        San Francisco, California
Loan No. 6 102 899                                             September 22,1998


FOR VALUE RECEIVED, the undersigned,  MISSION WEST PROPERTIES,  L.P., a Delaware
limited  partnership,  MISSION  WEST  PROPERTIES,  L.P.  I, a  Delaware  limited
partnership,  MISSION WEST PROPERTIES,  L.P. II, a Delaware limited partnership,
and  MISSION  WEST  PROPERTIES,   L.P.  III,  a  Delaware  limited   partnership
(collectively,  "Maker"),  each  having  an  address  at  10050  Bandley  Drive,
Cupertino,  California 95014, and the general partner of each being Mission West
Properties,  a California  corporation,  JOINTLY AND SEVERALLY PROMISE TO PAY TO
THE  ORDER  OF  THE  PRUDENTIAL  INSURANCE  COMPANY  OF  AMERICA,  a New  Jersey
corporation ("Prudential"), authorized to do business in the State of California
(Prudential  and its  successors  and  assigns  who become  holders of this Note
hereinafter   collectively  referred  to  as  "Holder"),  by  "Electronic  Funds
Transfer" to Prudential at Bank of New York,  located in New York, New York, ABA
Routing Number 021-000-018, Account No. 890-0304-766, referencing Loan No. 6 102
899,  or at such  other  place as Holder  may from time to time  designate,  the
principal   sum  of  One  Hundred   Thirty   Million   United   States   Dollars
($130,000,000.00),  together with interest thereon from the Initial Disbursement
Date  hereunder  through the date the Loan is paid in full,  at a rate per annum
equal to the Interest Rate.

1.  DEFINITIONS.  The  following  terms shall have the meanings set forth below.
Capitalized  terms not otherwise  defined herein shall have the meaning ascribed
to such terms in the other Loan Documents.

     DEED OF TRUST:  That certain  Deed of Trust,  Security  Agreement,  Fixture
     Filing with Assignment of Rents and Proceeds of even date herewith executed
     by Maker as  "Trustor" to the benefit of  Prudential  as  "Beneficiary"  as
     security for repayment of this Note.

     DISCOUNT  RATE:  The  interest  rate which,  when  compounded  monthly,  is
     equivalent to the Treasury Rate when compounded semi-annually.

     INITIAL DISBURSEMENT DATE: The date of this Note.

     INTEREST RATE: A rate of interest per annum of six and fifty-six hundredths
     percent (6.56%).

     LOAN DOCUMENTS: As defined in the Deed of Trust.

     MATURITY DATE: October 15, 2008.

     NOTE: This Promissory Note.

     PREPAYMENT  AMOUNT:  The  amount  of the  Principal  Balance  prepaid  on a
     Prepayment Date.

     PREPAYMENT  DATE: Any date,  prior to the Maturity Date,  upon which all or
     any portion of the Principal Balance is prepaid.

     PREPAYMENT PREMIUM: As defined in Paragraph 6(a).

     PRESENT  VALUE  OF  THE  PREPAYMENT   AMOUNT:   The  amount  determined  by
     discounting all scheduled  payments of principal and interest  remaining to
     the Maturity Date,  attributable to the Prepayment  Amount, at the Discount
     Rate.  If the  Prepayment  Date  occurs on a date  other  than a  regularly
     scheduled payment date under this Note, the actual number of days remaining
     from the Prepayment Date to the next regularly scheduled payment date shall
     be used to discount within this period.

     PRIME  RATE:  The  base  rate  on  corporate   loans  posted  by  at  least
     seventy-five  percent (75%) of the twenty (20) largest United States banks,
     designated  and published as the "Prime Rate" in the Wall Street Journal on
     the date an Event of Default occurs.

     PRINCIPAL  BALANCE:  The  principal  balance of this Note from time to time
     outstanding.

     SECONDARY  INTEREST  RATE: A rate of interest per annum equal to the lesser
     of (i) the maximum rate  allowed to be charged by Holder  under  applicable
     law,  or (ii) the  greater  of (A) the sum of the  Interest  Rate plus five
     percent (5%), or (B) the sum of the Prime Rate plus five percent (5%).

     TERM: The term of the Loan, commencing on the Initial Disbursement Date and
     ending on the Maturity Date.

     TREASURY RATE: The interest rate, conclusively determined by Holder, in its
     sole discretion,  on the Prepayment Date, equal to the semi-annual yield on
     the Treasury  Constant Maturity Series with maturity equal to the remaining
     weighted  average  life of the Loan for the  week  prior to the  Prepayment
     Date, as reported in Federal  Reserve  Statistical  Release H.15 - Selected
     Interest Rates, such yield being determined by linear interpolation between
     the yields  reported in Release H.15,  if necessary.  If Release H.15 is no
     longer published, Holder shall select a comparable publication to determine
     the Treasury Rate.

2. PAYMENTS. On the fifteenth day of November,  1998, an amount equal to the sum
of (a) all accrued interest,  at the Interest Rate, on the Principal Balance for
the period from the Initial  Disbursement Date through and including October 14,
1998,  and (b) a monthly  installment of principal and interest in the amount of
Eight Hundred Twenty-Six  Thousand Eight Hundred  Twenty-Four and 80/100 Dollars
($826,824.80),  shall be due and payable. Commencing on the fifteenth day of the
December,  1998,  and  continuing on the  fifteenth  day of each calendar  month
thereafter  through and including the Maturity  Date,  monthly  installments  of
principal and interest in the amount of Eight Hundred Twenty-Six  Thousand Eight
Hundred  Twenty-Four and 80/100 Dollars  ($826,824.80) shall be due and payable.
The entire unpaid  Principal  Balance,  plus accrued  interest and other amounts
payable under the Loan Documents, shall be due and payable on the Maturity Date.

3.     TREATMENT OF PAYMENTS.

      (a) Until directed otherwise in writing by Holder, all payments made under
      this Note shall be made by Electronic  Funds Transfer from Maker's account
      at an Automated  Clearing House member bank  satisfactory to Holder in its
      sole  discretion.  Maker shall  direct such bank in writing so to transfer
      payments on their due dates to Holder's designated  account.  Each payment
      shall be  initiated by Holder by  Electronic  Funds  Transfer  through the
      Automated  Clearing  House network for  settlement on each  respective due
      date.  Prior to each payment due date, Maker shall deposit and/or maintain
      sufficient  funds in Maker's  account to cover each debit entry to Maker's
      account.

      (b) Holder's approval and designation of a bank (or banks) under PARAGRAPH
      3(A)  above  shall  be  confirmed  in  writing.  Notwithstanding  Holder's
      approval  of a bank under  PARAGRAPH  3(A)  above,  Holder  shall have the
      right, upon thirty (30) days prior written notice to Maker, (i) to require
      Maker to use a  different  bank that is mutually  acceptable  to Maker and
      Holder, or (ii) to designate a different account for Holder.  All costs of
      establishing  and  maintaining  these  accounts  and all  costs  of  these
      Electronic Funds Transfers shall be paid by Maker.

      (c) For purposes of  calculating  interest  under this Note, a year of 360
      days  consisting  of twelve (12) thirty (30) days months shall be employed
      regardless of the actual time elapsed.

      (d) All payments due under this Note or the Loan  Documents  shall be paid
      by Maker in lawful money of the United  States of America on the date such
      payment is due. All such payments shall be made without  deduction for any
      present or future  taxes,  levies,  deductions,  charges  or  withholdings
      (including Federal,  state or local income taxes),  which amounts shall be
      paid by Maker.

      (e) Payments  from Maker to Holder under this Note shall be applied  first
      to any expense reimbursements under the Loan Documents,  then to any Daily
      Charges or Late  Charges,  as the case may be,  then to accrued and unpaid
      interest,  and the balance to the  Principal  Balance  and any  Prepayment
      Premium due thereon.

4. DAILY CHARGES; LATE CHARGES; SECONDARY INTEREST RATE.

     (a) If Maker fails timely to pay any sum due and payable under this Note on
     or before the date due, a late charge equal to Eight  Hundred Fifty Dollars
     ($850.00) per day (the "Daily  Charge") shall be due for each day that such
     sum is not paid (including, the day upon which the payment is made), but if
     such sum, together with the Daily Charges applicable  thereto,  is not paid
     by the fourteenth  (14th) day after the date such sum is due, a late charge
     equal to four cents  ($0.04) for each dollar  ($1.00) of each such sum (the
     "Late Charge")  shall be  immediately  due and payable in lieu of all Daily
     Charges.  Maker  acknowledges  and agrees  that its  failure to make timely
     payments will result in Holder  incurring  additional  expense in servicing
     the Loan, and that it is extremely  difficult and  impractical to ascertain
     the extent of such  damages  and that the Daily  Charge or the Late  Charge
     represent  a  fair  and  reasonable   estimate,   considering  all  of  the
     circumstances  existing on the date of the  execution of this Note,  of the
     costs that Holder will incur by reason of such late payment.  Acceptance of
     any  Daily  Charge or Late  Charge  shall  not  constitute  a waiver of the
     default with respect to the late payment, and shall not prevent Holder from
     exercising  any of the other rights or remedies  available  hereunder or at
     law or in equity.

     (b) Maker  further  acknowledges  and agrees  that during the time that any
     payment of principal, interest or other amount due under this Note shall be
     delinquent, Holder will incur additional costs and expenses attributable to
     its loss of use of the money  due and to the  adverse  impact  on  Holder's
     ability  to  meet  its  other   obligations   and  avail  itself  of  other
     opportunities.  Maker agrees that it is extremely difficult and impractical
     to ascertain the extent of such expenses,  and Maker therefore  agrees that
     upon the  occurrence  of an Event of  Default,  interest  at the  Secondary
     Interest Rate shall accrue on the Indebtedness, regardless of whether there
     has been an acceleration of the maturity of the Indebtedness.

5.  EVENT OF  DEFAULT.  The  occurrence  of an Event of  Default  under any Loan
Document  shall  constitute  an Event  of  Default  under  this  Note.  Upon the
occurrence of an Event of Default, including the failure of the Maker to observe
the provisions of Paragraph 4.2 of the Deed of Trust, Holder, at its option, may
cause the Principal  Balance,  together with all unpaid  accrued  interest,  any
Prepayment  Premium and any other sums  evidenced or secured by this Note or any
Loan Document,  to be immediately due and payable,  without further presentment,
demand, protest or notice of any kind, by so notifying Maker in writing.

6.  PREPAYMENT.

      (a) If for any reason the Principal Balance or any portion thereof is paid
      prior  to  the  Maturity  Date,  whether  voluntarily,  involuntarily,  by
      operation of law,  acceleration,  including  acceleration on account of an
      Event of Default and/or a violation of Paragraph 4.2 of the Deed of Trust,
      or  otherwise,  but  excluding  any  prepayment  made  as  result  of  the
      application  by Holder of  insurance  proceeds or  condemnation  awards as
      provided  by the terms of the Loan  Documents,  Maker shall pay to Holder,
      together  with  the  subject  Prepayment  Amount  and any  unpaid  accrued
      interest,  a prepayment  charge (the  "Prepayment  Premium")  equal to the
      greater of:

           (i) the  product of (A) one  percent  (1%) of the  Prepayment  Amount
           multiplied by (B) a fraction, the numerator of which is the number of
           full months  remaining  until the Maturity Date as of the  Prepayment
           Date  and the  denominator  of  which is the  number  of full  months
           comprising the Term of the Loan; or

           (ii) the Present Value of the  Prepayment  Amount less the sum of (A)
           the  Prepayment  Amount,  and (B) unpaid  accrued  interest,  if any,
           calculated as of the Prepayment Date.

      (b) Maker shall have the right voluntarily to prepay all or any portion of
      the Principal Balance, together with accrued interest thereon, but only if
      Maker gives Holder not less than thirty (30) days' prior written notice of
      its  intention  to  prepay,  and  delivers  to  Holder,  on or before  the
      Prepayment Date, the Prepayment Premium as calculated above, together with
      the  Prepayment  Amount and all accrued  interest and other sums due under
      the Loan Documents.  Notwithstanding  the foregoing,  Maker shall have the
      right to prepay the  Principal  Balance,  together  with accrued  interest
      thereon,  without payment of the Prepayment Premium,  during the period of
      time commencing fourteen (14) days immediately prior to the Maturity Date.

      (c) Maker  acknowledges  that (i) the  Prepayment  Premium  represents the
      reasonable estimate of Holder and Maker of a fair average compensation for
      the loss that may be  sustained by Holder due to the payment of any of the
      Principal Balance prior to the Maturity Date; (ii) the Prepayment  Premium
      shall be paid  without  prejudice  to the right of Holder to  collect  any
      other  amounts  provided  to be paid  hereunder  or under the  other  Loan
      Documents;  and (iii) Holder  shall not be obligated to actually  reinvest
      the Prepayment  Amount in any Treasury  Constant  Maturity Series or other
      specific investments as a condition to receiving the Prepayment Premium.

      (d) Maker acknowledges that it is comprised of four (4) different Persons,
      each of which owns  separately its Property,  and that the Loan is secured
      by the interest of all Persons  comprising  Maker in all of the  Property.
      Maker further acknowledges that in connection  therewith,  for purposes of
      allocating the Loan proceeds  appropriately  among the Persons  comprising
      Maker and their  respective  Property,  Maker and Holder agree to allocate
      the Loan proceeds in accordance with the Original Allocated Loan Amount as
      set  forth in  Exhibit  B to the Deed of  Trust  in  order to  ensure  the
      continuing adequacy of the security interest of Holder in each Property of
      Maker under the Loan  Documents.  Maker agrees that any  prepayment of the
      Loan,  unless otherwise  provided in the Loan Documents,  shall be applied
      pro rata  against  the  Original  Allocated  Loan  Amount (as set forth in
      Exhibit B to the Deed of Trust) of each Property.

      (e) Maker hereby  expressly  waives any right it may have under California
      Civil  Code  Section  2954.10 to prepay  this  Note,  in whole or in part,
      without  payment  of the  Prepayment  Premium,  upon  acceleration  of the
      Maturity  Date  of this  Note,  and  agrees  that  if for  any  reason,  a
      prepayment  of any or all of  this  Note  is  made,  whether  voluntarily,
      involuntarily  or upon or following any  acceleration of the Maturity Date
      of this  Note by  Holder,  then  Maker  shall pay the  Prepayment  Premium
      calculated pursuant to PARAGRAPH 6(a). By initialing this provision in the
      space provided below, Maker hereby declares that the Holder's agreement to
      make the Loan at the Interest Rate and for the Term set forth in this Note
      constitutes adequate consideration,  given individual weight by Maker, for
      this waiver and agreement.

                          INITIALS OF MAKER:  ____________________

7.  SECURITY.  This Note is  secured  by the Deed of Trust  and the  other  Loan
Documents, which contain provisions for the acceleration of the maturity of this
Note upon the occurrence of certain described events.

8.  HOLDER'S  RIGHTS;  NO WAIVER BY HOLDER.  The rights,  powers and remedies of
Holder  under this Note shall be in addition to all rights,  powers and remedies
given to Holder  under the Loan  Documents  and any other  agreement or document
securing or evidencing the  Indebtedness  or by virtue of any statute or rule of
law, including the California  Uniform Commercial Code. All such rights,  powers
and  remedies  shall  be  cumulative  and  may  be  exercised   successively  or
concurrently in Holder's sole discretion  without  impairing  Holder's  security
interest,  rights or available  remedies.  Any forbearance,  failure or delay by
Holder in  exercising  any right,  power or remedy  shall not  preclude  further
exercise thereof,  and every right,  power or remedy of Holder shall continue in
full force and effect until such right,  power or remedy is specifically  waived
in a writing executed by Holder. Maker waives any right to require the Holder to
proceed  against any Person or to exhaust all or any part of the  Property or to
pursue any remedy in Holder's power.

9. MAKER'S WAIVERS.

      (a) Maker and any endorsers of this Note,  and each of them,  hereby waive
      diligence, demand, presentment for payment, notice of non-payment, protest
      and notice of protest, and specifically consent to and waive notice of any
      renewals or extensions of this Note,  whether made to or in favor of Maker
      or any other  person or  persons.  Maker  and any  endorsers  of this Note
      expressly waive all right to the benefit of any statute of limitations and
      any moratorium,  reinstatement,  marshaling,  forbearance,  extension,  or
      appraisement now or hereafter provided by the Constitution and the laws of
      the  United  States and of any state  thereof,  as a defense to any demand
      against Maker or any such  endorsers,  to the fullest extent  permitted by
      law.

      (b) Maker  hereby  waives  any right to trial by jury with  respect to any
      action or proceeding brought by Holder or any other Person relating to (i)
      the Obligations, or (ii) the Loan Documents. Maker hereby agrees that this
      Note  constitutes a written consent to waiver of trial by jury pursuant to
      the provisions of California Code of Civil Procedure Section 631 and Maker
      does  hereby   constitute   and   appoint   Holder  its  true  and  lawful
      attorney-in-fact, which appointment is coupled with an interest, and which
      shall survive the dissolution or bankruptcy of any Maker, or any Transfer,
      and Maker does hereby authorize and empower Holder, in the name, place and
      stead of Maker,  to file this Note with the clerk or judge of any court of
      competent  jurisdiction as statutory written consent to waiver of trial by
      jury.

10. TRANSFERS BY HOLDER. This Note, or any interest in this Note and/or the Loan
Documents,  may be  hypothecated,  transferred or assigned by Holder without the
prior consent of Maker.

11.  AMENDMENT.  This Note may be amended or modified  only by an  instrument in
writing  which by its  express  terms  refers  to this  Note  and  which is duly
executed by the party sought to be bound thereby.

12.  SUCCESSORS  AND  ASSIGNS.  This Note shall be binding upon and inure to the
benefit  of  the  parties  hereto  and  their   respective   heirs,   executors,
administrators, personal representatives, successors and permitted assigns.

13.  GOVERNING  LAW.  This Note shall be governed by and construed in accordance
with the laws of the State of California.

14.  TIME.  Time is of the  essence  with  respect  to each and  every  term and
provision of this Note.

15.  USURY.  Notwithstanding  any  provision  herein,  the total  liability  for
payments in the nature of interest, additional interest, or other charges, under
this Note or any other Loan  Document,  shall not exceed the  applicable  limits
imposed by any  applicable  state or  Federal  interest  rate laws.  If any such
payments in the nature of interest,  additional interest, and other charges made
hereunder  or under any  other  Loan  Documents  are held to be in excess of the
applicable  limits imposed by any applicable state or Federal laws, it is agreed
that  any such  amount  held to be in  excess  shall be  considered  payment  of
principal  and the  Principal  Balance  shall be reduced  by such  amount in the
inverse order of maturity so that the total liability for payments in the nature
of  interest,  additional  interest  and other  charges,  shall never exceed the
applicable  limits imposed by any applicable state or Federal interest rate laws
in compliance with the desires of Holder and Maker as set forth herein.

16.  NOTICES.  All  notices,  consents  and  other  communications  required  or
permitted  by this Note shall be in writing and shall be given in the manner set
forth in the Deed of Trust.

17. ATTORNEYS' FEES. If any arbitration,  litigation or similar  proceedings are
brought by either party to enforce any  obligation or to pursue any remedy under
this Note, the party prevailing in any such  arbitration,  litigation or similar
proceedings  will be entitled to costs of  collection,  if any,  and  reasonable
attorneys fees incurred in connection with such proceedings and in collecting or
enforcing any award granted therein.

18.  LIMITATION ON PERSONAL LIABILITIES.

      (a) Except as  expressly  set forth in  PARAGRAPHS  18(B) AND 18(C) below,
      neither   Maker  nor  any  general   partner  of  Maker   (singularly   or
      collectively,  the "Exculpated Parties") shall have any personal liability
      for the Loan or any Obligations  set forth in the Loan  Documents,  except
      that Holder shall be entitled to bring a foreclosure  action or proceeding
      or other appropriate action or proceeding to enforce the Loan Documents or
      foreclose or realize upon and/or  protect the Property  (including  naming
      the Exculpated Parties in such actions or proceedings)  and/or to draw on,
      and retain the proceeds of, any letter of credit issued in favor of Holder
      with respect to the Loan.

      (b) Notwithstanding  anything to the contrary contained in this Note or in
      any Loan Document,  Holder shall be entitled to proceed personally against
      the Exculpated  Parties,  or any of them, for, and the Exculpated  Parties
      shall have personal liability jointly and severally for:

           (i) any  indemnity,  guaranty,  or similar  instrument  furnished  in
           connection with the Loan (including the ERISA provisions of Paragraph
           9.18 of the Deed of Trust and the Hazardous Substances Agreement);

           (ii) any  assessments  and/or taxes  (accrued  and/or  payable)  with
           respect to the  Property to the extent  income from the  Property has
           been used other than in accordance with the Loan Documents;

           (iii) any security  deposits of tenants (1) not turned over to Holder
           upon foreclosure,  sale (pursuant to power of sale), or conveyance in
           lieu thereof, or (2) not turned over to a receiver or trustee for the
           Property after his/her appointment;

           (iv) any insurance  proceeds or  condemnation  awards  neither turned
           over to  Holder  nor used in  compliance  with the  terms of the Loan
           Documents;

           (v) if any  of  the  Exculpated  Parties  executes  an  amendment  or
           termination  of any Lease  (other  than a Lease  with a Major  Tenant
           which is governed by  Paragraph  18(c)(iv)  below)  without the prior
           written  consent of Holder,  if such  consent is  required  under the
           terms  of the Loan  Documents,  the  Exculpated  Parties  shall  have
           personal liability for the greater of:

                  (1) the present value (calculated at the Discount Rate) of the
                  aggregate total dollar amount (if any) by which (A) the rental
                  income and/or other tenant  obligations prior to the amendment
                  or  termination  of such Lease,  exceeds (B) the rental income
                  and/or  other  tenant   obligations  after  the  amendment  or
                  termination of such Lease, or

                  (2)  any  termination  fee  or  other  consideration  paid  in
                  connection with such amendment or termination;

           (vi)   waste of the Property;

           (vii) any rents or other income from the Property  received by any of
           the Exculpated  Parties  following a default under the Loan Documents
           and not otherwise  applied to the Indebtedness or to the current (and
           not  deferred)  operating  expenses of the  Property  incurred in the
           ordinary course,  excluding  amounts paid as operating  expenses to a
           Person related to or affiliated  with any of the  Exculpated  Parties
           unless  payment of such  amounts are  expressly  permitted  under the
           terms of the Loan Documents;

                  (viii)  Maker's  failure  to  maintain  any  letter  of credit
           required  under  the  terms of the Loan  Documents  or  otherwise  in
           connection with the Loan;

                  (ix) Maker's  obligation to indemnify  Holder for  commissions
           and fees under Paragraph 2.10 of the Deed of Trust; and/or

           (x) all legal  fees  (including  allocated  costs of  Holder's  staff
           attorneys)  and other  expenses  incurred by Holder in enforcing  the
           Loan Documents if any Exculpated Party contests, delays, or otherwise
           hinders  or  opposes   (including  the  filing  of  a  bankruptcy  or
           insolvency proceeding) any of Holder's enforcement actions.

      (c)  Except  as  provided  in  Paragraph  18(c)(v)  below,  the  agreement
      contained  in this  Paragraph  18 to limit the  personal  liability of the
      Exculpated  Parties  shall become null and void and of no further force or
      effect,  and the Exculpated  Parties shall have personal liability for all
      Indebtedness  and all  Obligations  evidenced  by the  Note  and the  Loan
      Documents, in the event:

           (i)    there is any breach or violation of Paragraph
           4.2 of the Deed of Trust;

           (ii) there is any fraud or material  misrepresentation  by any of the
           Exculpated  Parties  in  connection  with  the  Property,   the  Loan
           Documents, the Application, or any other aspect of the Loan;

           (iii) the  Property  or any part  thereof  becomes  an asset in (1) a
           voluntary bankruptcy or insolvency proceeding, or (2) any involuntary
           bankruptcy or  insolvency  proceeding  which is not dismissed  within
           ninety  (90) days of filing,  except  that this  clause (2) shall not
           apply if such involuntary bankruptcy is filed by Holder;

           (iv) any Exculpated Party executes an amendment or termination of any
           Lease  with a Major  Tenant  without  the prior  written  consent  of
           Holder,  if such  consent  is  required  under  the terms of the Loan
           Documents; or

           (v) the Property or any individual property constituting the Property
           is rendered  "environmentally  impaired",  as such term is defined in
           Section 726.5 of the California  Code of Civil  Procedure;  provided,
           however,  that in such  event,  the  Exculpated  Parties  shall  have
           personal  liability  only  for the  Original  Allocated  Loan  Amount
           allocated  to  the  Property   that  is  or  are   determined  to  be
           "environmentally impaired",  unless, in so limiting Holder's recourse
           to less than all Indebtedness  and all  Obligations,  Holder would be
           substantially  deprived of the  benefits  available  to Holder  under
           Section 726.5.

IN WITNESS  WHEREOF,  Maker has caused  this Note to be executed  and  delivered
effective as of the date first written above.

                               MAKER:

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

                               By: Mission West Properties,
                                   a California corporation, its general partner

                                       By:
                                         --------------------------------------
                                         Carl E. Berg, Chairman, President, CEO

                              [Signatures continued on succeeding page]
                              MISSION WEST PROPERTIES, L.P. I,
                              a Delaware limited partnership

                              By: Mission West Properties,
                                  a California corporation, its general partner

                                       By:
                                         --------------------------------------
                                         Carl E. Berg, Chairman, President, CEO


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

                               By:Mission West Properties,
                                  a California corporation, its general partner

                                       By:
                                         --------------------------------------
                                         Carl E. Berg, Chairman, President, CEO


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

                               By:Mission West Properties,
                                  a California corporation, its general partner

                                       By:
                                         --------------------------------------
                                         Carl E. Berg, Chairman, President, CEO