Exhibit 99.1


                             CERTIFICATE PURSUANT TO
                 RULE 13a-14 THE SECURITIES EXCHANGE ACT OF 1934

I, Carl E. Berg, certify that:

1.  I have  reviewed  this  Quarterly  Report  on  Form  10-Q  of  Mission  West
Properties, Inc. (the "Company") for the quarterly period ended March 31, 2003;

2. Based on my  knowledge,  this  quarterly  report  does not contain any untrue
statement of a material fact or omit to state a material fact  necessary to make
the statements made, in light of the  circumstances  under which such statements
were made, not  misleading  with respect to the period covered by this quarterly
report;

3.  Based  on my  knowledge,  the  financial  statements,  and  other  financial
information  included in this quarterly  report,  fairly present in all material
respects the financial  condition,  results of operations  and cash flows of the
registrant as of, and for, the periods presented in this quarterly report;

4.  The  registrant's  other  certifying  officers  and  I are  responsible  for
establishing and maintaining  disclosure  controls and procedures (as defined in
Exchange Act Rules 13a-14 and 15d-14) for the registrant and we have:

     a)   designed  such  disclosure  controls  and  procedures  to  ensure  the
          material  information  relating  to  the  registrant,   including  its
          consolidated subsidiaries,  is made known to us by others within those
          entities,  particularly  during  the  period in which  this  quarterly
          report is being prepared;
     b)   evaluated the  effectiveness of the registrant's  disclosure  controls
          and procedures as of a date within 90 days prior to the filing date of
          this quarterly report (the "Evaluation Date"); and
     c)   presented  in  this  quarterly   report  our  conclusions   about  the
          effectiveness  of the disclosure  controls and procedures based on our
          evaluation as of the Evaluation Date;

5. The registrant's other certifying officers and I have disclosed, based on our
most recent evaluation,  to the registrant's auditors and the audit committee of
registrant's board of directors (or persons performing the equivalent function):

     a)   all  significant  deficiencies  in the design or operation of internal
          controls  which could  adversely  affect the  registrant's  ability to
          record,  process,   summarize  and  report  financial  data  and  have
          identified for the  registrant's  auditors any material  weaknesses in
          internal controls; and
     b)   any fraud, whether or not material,  that involves management or other
          employees who have a  significant  role in the  registrant's  internal
          controls; and

6. The  registrant's  other  certifying  offices  and I have  indicated  in this
quarterly  report  whether or not there  were  significant  changes in  internal
controls or in other factors that could  significantly  affect internal controls
subsequent to the date of our most recent  evaluation,  including any corrective
actions with regard to significant deficiencies and material weaknesses.


Carl E. Berg
Chairman and CEO

May 14, 2003