Exhibit 3.3

                   CERTIFICATE OF DETERMINATION OF PREFERENCES
                                       OF
                      8 7/8% SERIES X CUMULATIVE REDEEMABLE
                                 PREFERRED STOCK
                                       OF
                             PS BUSINESS PARKS, INC.

            [As filed in the office of the Secretary of State of the
                    State of California on September 7, 1999]

        The undersigned, David Goldberg and Jack E. Corrigan, Vice President and
Secretary,  respectively,  of PS BUSINESS PARKS, INC., a California corporation,
do hereby certify:

        FIRST:  The  Restated  Articles  of  Incorporation  of  the  Corporation
authorize  the  issuance of  50,000,000  shares of stock  designated  "preferred
shares,"  issuable  from time to time in one or more series,  and  authorize the
Board of Directors to fix the number of shares constituting any such series, and
to determine or alter the dividend  rights,  dividend rate,  conversion  rights,
voting  rights,   right  and  terms  of  redemption   (including   sinking  fund
provisions),  the redemption  price or prices and the liquidation  preference of
any wholly  unissued series of such preferred  shares,  and the number of shares
constituting any such series.

        SECOND:  The Board of  Directors of the  Corporation  did duly adopt the
resolutions  attached hereto as Exhibit A and  incorporated  herein by reference
authorizing and providing for the creation of a series of preferred shares to be
known as "8 7/8% Series X Cumulative  Redeemable  Preferred Stock" consisting of
1,200,000 shares, none of the shares of such series having been issued.

        We further  declare under penalty of perjury under the laws of the State
of  California  that the  matters  set  forth in this  certificate  are true and
correct of our own knowledge.

        IN WITNESS WHEREOF,  the undersigned have executed this certificate this
7th day of September, 1999.


                                        /s/ David Goldberg
                                        --------------------------
                                        David Goldberg, Vice President


                                        /s/ Jack E. Corrigan
                                        --------------------------
                                        Jack E. Corrigan, Secretary




                                    EXHIBIT A

                      RESOLUTION OF THE BOARD OF DIRECTORS
                           OF PS BUSINESS PARKS, INC.

                    ESTABLISHING A SERIES OF 8 7/8% SERIES X
                      CUMULATIVE REDEEMABLE PREFERRED STOCK


        RESOLVED  that  pursuant to the  authority  conferred  upon the Board of
Directors  by Article  III of the  Restated  Articles of  Incorporation  of this
Corporation,  there is hereby  established a series of the authorized  preferred
shares of this  Corporation  having a par value of $.01 per share,  which series
shall be  designated 8 7/8% Series X  Cumulative  Redeemable  Preferred  Stock,"
shall  consist  of  1,200,000  shares  and  shall  have  the  following  rights,
preferences and privileges:

        1. Rank. The 8 7/8% Series X Cumulative  Redeemable Preferred Stock (the
"Series X Preferred  Stock") will, with respect to distributions and rights upon
voluntary  or  involuntary   liquidation,   winding-up  or  dissolution  of  the
Corporation,  or both, rank senior to all classes or series of Common Shares and
to all  classes  or  series  of  equity  securities  of the  Corporation  now or
hereafter authorized,  issued or outstanding,  other than any class or series of
equity securities of the Corporation expressly designated as ranking on a parity
with or senior to the Series X Preferred  Stock as to  distributions  and rights
upon  voluntary or  involuntary  liquidation,  winding-up or  dissolution of the
Corporation. For purposes of this Certificate of Determination, the term "Parity
Preferred  Stock" shall be used to refer to any class or series of capital stock
of the Corporation now or hereafter authorized,  issued or outstanding expressly
designated by the  Corporation to rank on a parity with Series X Preferred Stock
with  respect  to  distributions   and  rights  upon  voluntary  or  involuntary
liquidation,  winding-up  or  dissolution  of  the  Corporation  (including  the
Corporation's  9 1/4%  Cumulative  Preferred  Stock,  Series A, 8-7/8%  Series B
Cumulative Redeemable Preferred Stock, and 8 3/4% Series C Cumulative Redeemable
Preferred Stock). For purposes of the preceding sentence,  "capital stock" means
any equity securities  (including  Common Shares and Preferred  Stock),  shares,
participation or other ownership  interests (however  designated) and any rights
(other  than  debt  securities  convertible  into  or  exchangeable  for  equity
securities) or options to purchase any of the foregoing.

        2. Distributions  Rights.  (a) Payment of Distributions.  Subject to the
rights of holders of Parity Preferred Stock as to the payment of  distributions,
holders of Series X  Preferred  Stock  shall be entitled to receive the Series X
Priority  Return,  when,  as and if  declared by the Board of  Directors  of the
Corporation,  out of funds legally  available for the payment of  distributions.
Such distributions  shall be cumulative,  shall accrue from the original date of
issuance of the Series X Preferred  Stock and will be payable (A)  quarterly  in
arrears,  on March  31,  June 30,  September  30 and  December  31 of each  year
commencing  on the  last  day of the  calendar  quarter  following  the  date of
issuance of such stock and, (B) in the event of a redemption,  on the redemption
date (each a "Series X  Preferred  Stock  Distribution  Payment  Date").  If any
Preferred  Stock  Distribution  Payment  Date is not a Business  Day (as defined
herein),  then payment of the distribution to be made on such date shall be made
on the Business Day  immediately  preceding  such Preferred  Stock  Distribution
Payment  Date in each  case with the same  force  and  effect as if made on such
date.  Distributions on the Series X Preferred Stock will be made to the holders
of record of the Series X Preferred  Stock on the  relevant  record  dates to be
fixed by the Board of Directors of the Corporation,  which record dates shall in
no event be more than 45 days or less than 15 days prior to the relevant  Series
X Preferred Stock Distribution Payment Date (each a "Distribution Record Date").

        For purposes of this Certificate of  Determination,  the following terms
shall have the meanings set forth herein:  (i)  "Liquidation  Preference"  shall
mean, with respect to the Series X Preferred Stock, $25.00 per share of Series X
Preferred Stock, plus the amount of any accumulated and unpaid Series X Priority
Return (as  hereinafter  defined)  with  respect to such  share,  whether or not
declared, minus any distributions in excess of the Series X Priority Return that
has  occurred  with  respect to such  Series X Preferred  Units,  to the date of
payment;  (ii) "Series X Priority  Return" shall mean an amount equal to 8?% per
annum of the  Liquidation  Preference  per  share of Series X  Preferred  Stock,
commencing  on the date of issuance  of such share of Series X Preferred  Stock,
determined  on the basis of a 365-day  year (and  actual  days for any  period),
cumulative  to the  extent  not  distributed  on any  Series X  Preferred  Stock
Distribution  Payment Date; and (iii)  "Business Day" shall mean each day, other
than a Saturday or a Sunday, which is not a day on which banking institutions in
New York,  New York are  authorized or required by law,  regulation or executive
order to close.

      (b) Prohibition on Distributions. No distributions on Series X Preferred
Stock shall be authorized by the Board of Directors of the  Corporation  or paid
or set apart for  payment by the  Corporation  at any such time as the terms and
provisions of any agreement of the Corporation  including any agreement relating
to  indebtedness,  prohibits  such  authorization,  payment or setting apart for
payment or  provides  that such  authorization,  payment  or  setting  apart for
payment would  constitute a breach  thereof or a default  thereunder,  or to the
extent that such  authorization  or payment shall be restricted or prohibited by
law.

        (c)  Distributions  Cumulative.  Distributions on the Series X Preferred
Stock will accrue  whether or not the terms and  provisions  of any agreement of
the  Corporation,  including any agreement  relating to its  indebtedness at any
time  prohibits  the  current  payment  of  distributions,  whether  or not  the
Corporation has earnings,  whether or not there are funds legally  available for
the  payment of such  distributions  and whether or not such  distributions  are
authorized  or  declared.  Accrued  but  unpaid  distributions  on the  Series X
Preferred Stock will accumulate as of the Series X Preferred Stock  Distribution
Payment Date on which they first  become  payable.  Distributions  on account of
arrears for any past distribution  periods may be declared and paid at any time,
without  reference to a regular Series X Preferred  Stock  Distribution  Payment
Date to  holders of record of the Series X  Preferred  Stock on the record  date
fixed by the Board of  Directors  which  date  shall not be more than 45 days or
less  than  15  days  prior  to  the  payment  date.   Accumulated   and  unpaid
distributions will not bear interest.

        (d) Priority as to Distributions.  (i) So long as any Series X Preferred
Stock  is  outstanding,  no  distribution  of cash or  other  property  shall be
authorized,  declared,  paid or set apart for payment on or with  respect to any
class or series of  Common  Shares or any class or series of other  stock of the
Corporation  ranking  junior as to the payment of  distributions  or rights upon
voluntary  or  involuntary   dissolution,   liquidation  or  winding-up  of  the
Corporation to the Series X Preferred  Stock (such Common Shares or other junior
stock,  collectively,  "Junior Stock"),  nor shall any cash or other property be
set aside for or applied to the purchase,  redemption or other  acquisition  for
consideration of any Series X Preferred Stock, any Parity Preferred Stock or any
Junior Stock, unless, in each case, all distributions  accumulated on all Series
X Preferred  Stock and all classes and series of  outstanding  Parity  Preferred
Stock have been paid in full.  The  foregoing  sentence  shall not  prohibit (i)
distributions  payable solely in Junior Stock, and (ii) the conversion of Series
X Preferred  Stock,  Junior  Stock or Parity  Preferred  Stock into stock of the
Corporation ranking junior to the Series X Preferred Stock as to distributions.

        (ii) So long as  distributions  have  not  been  paid in full  (or a sum
sufficient  for such full  payment  is not  irrevocably  deposited  in trust for
payment) upon the Series X Preferred  Stock,  all  distributions  authorized and
declared  on the  Series  X  Preferred  Stock  and  all  classes  or  series  of
outstanding  Parity  Preferred  Stock  with  respect to  distributions  shall be
authorized  and  declared  so that the amount of  distributions  authorized  and
declared per share of Series X Preferred  Stock and such other classes or series
of Parity  Preferred  Stock shall in all cases bear to each other the same ratio
that accrued  distributions  per share on the Series X Preferred  Stock and such
other classes or series of Parity  Preferred  Stock (which shall not include any
accumulation in respect of unpaid  distributions for prior distribution  periods
if such  class or  series  of  Parity  Preferred  Stock  do not have  cumulative
distribution rights) bear to each other.

        (e) No Further Rights.  Holders of Series X Preferred Stock shall not be
entitled  to any  distributions,  whether  payable in cash,  other  property  or
otherwise, in excess of the full cumulative distributions described herein.

        3. Liquidation. (a) Payment of Liquidating Distributions. Subject to the
rights of holders of Parity  Preferred  Stock  with  respect to rights  upon any
voluntary  or  involuntary   liquidation,   dissolution  or  winding-up  of  the
Corporation  and subject to any series of capital  stock  ranking  senior to the
Series  X  Preferred  Stock  with  respect  to  rights  upon  any  voluntary  or
involuntary  liquidation,  dissolution  or  winding-up of the  Corporation,  the
holders of Series X  Preferred  Stock  shall be  entitled  to receive out of the
assets of the  Corporation  legally  available for  distribution or the proceeds
thereof,  after  payment or  provision  for debts and other  liabilities  of the
Corporation, but before any payment or distributions of the assets shall be made
to  holders  of  Common  Shares  or any  other  class or series of shares of the
Corporation  that ranks junior to the Series X Preferred Stock as to rights upon
liquidation,  dissolution or winding-up of the  Corporation,  an amount equal to
the Liquidation  Preference per share of Series X Preferred  Stock. If upon such
voluntary or  involuntary  liquidation,  dissolution  or  winding-up,  there are
insufficient  assets to permit full payment of liquidating  distributions to the
holders of Series X Preferred Stock and any Parity  Preferred Stock as to rights
upon liquidation,  dissolution or winding-up of the Corporation, all payments of
liquidating  distributions  on the  Series X  Preferred  Stock  and such  Parity
Preferred  Stock  shall be made so that the  payments  on the Series X Preferred
Stock and such Parity  Preferred Stock shall in all cases bear to each other the
same ratio that the respective  rights of the Series X Preferred  Stock and such
other  Parity  Preferred  Stock  (which  shall not include any  accumulation  in
respect of unpaid  distributions for prior  distribution  periods if such Parity
Preferred Stock does not have cumulative  distribution rights) upon liquidation,
dissolution or winding-up of the Corporation bear to each other.

        (b)  Notice.  Written  notice  of  any  such  voluntary  or  involuntary
liquidation,  dissolution or winding-up of the Corporation,  stating the payment
date or dates when, and the place or places where, the amounts  distributable in
such circumstances shall be payable, shall be given by (i) fax and (ii) by first
class mail,  postage pre-paid,  not less than 10 and not more than 60 days prior
to the  payment  date  stated  therein,  to each  record  holder of the Series X
Preferred  Stock at the  respective  addresses of such holders as the same shall
appear on the share transfer records of the Corporation.

        (c)  No  Further  Rights.  After  payment  of  the  full  amount  of the
liquidating  distributions  to which they are entitled,  the holders of Series X
Preferred  Stock will have no right or claim to any of the  remaining  assets of
the Corporation.

        (d) Consolidation,  Merger or Certain Other Transactions.  The voluntary
sale,  conveyance,  lease,  exchange  or  transfer  (for cash,  shares of stock,
securities or other  consideration)  of all or substantially all of the property
or  assets  of the  Corporation  to,  or the  consolidation  or  merger or other
business combination of the Corporation with or into, any corporation,  trust or
other  entity (or of any  corporation,  trust or other  entity  with or into the
Corporation)  or a statutory  share exchange shall not be deemed to constitute a
liquidation, dissolution or winding-up of the Corporation.

        4. Redemption.  (a) Right of Optional Redemption. The Series X Preferred
Stock may not be redeemed prior to September 7, 2004. On or after such date, the
Corporation  shall  have the right to redeem the Series X  Preferred  Stock,  in
whole  (but not in part),  at any  time,  upon not less than 30 nor more than 60
days'  written  notice,  at a redemption  price,  payable in cash,  equal to the
Liquidation Preference (the "Series X Redemption Price").

        (b)  Limitation  on  Redemption.  The  redemption  price of the Series X
Preferred  Stock will be  payable  solely to the extent  such  payment  would be
permitted as a distribution under the California Corporations Code.

        (c)  Procedures  for  Redemption.  (i) Notice of redemption  will be (i)
faxed, and (ii) mailed by the Corporation, postage prepaid, not less than 30 nor
more than 60 days prior to the  redemption  date,  addressed  to the  respective
holders  of record  of the  Series X  Preferred  Stock to be  redeemed  at their
respective  addresses as they appear on the transfer records of the Corporation.
No failure to give or defect in such  notice  shall  affect the  validity of the
proceedings  for the redemption of any Series X Preferred Stock except as to the
holder to whom such  notice was  defective  or not  given.  In  addition  to any
information  required by law or by the  applicable  rules of any  exchange  upon
which the Series X Preferred  Stock may be listed or  admitted to trading,  each
such notice shall state:  (i) the redemption  date,  (ii) the redemption  price,
(iii) the number of shares of Series X Preferred Stock to be redeemed,  (iv) the
place or  places  where  such  shares  of  Series X  Preferred  Stock  are to be
surrendered for payment of the redemption  price, (v) that  distributions on the
Series X  Preferred  Stock to be  redeemed  will  cease  to  accumulate  on such
redemption  date  and  (vi)  that  payment  of  the  redemption  price  and  any
accumulated  and  unpaid  distributions  will  be  made  upon  presentation  and
surrender of such Series X Preferred Stock.

        (ii) If the  Corporation  gives a notice of  redemption  in  respect  of
Series X Preferred Stock (which notice will be irrevocable) then, by 12:00 noon,
New York City  time,  on the  redemption  date,  the  Corporation  will  deposit
irrevocably  in trust for the  benefit of the  Series X  Preferred  Stock  being
redeemed funds sufficient to pay the applicable  Series X Redemption  Price, and
will give irrevocable instructions and authority to pay such Series X Redemption
Price to the  holders of the Series X  Preferred  Stock  upon  surrender  of the
certificate evidencing the Series X Preferred Stock by such holders at the place
designated  in the notice of  redemption.  On and after the date of  redemption,
distributions  will cease to accumulate  on the Series X Preferred  Stock called
for redemption,  unless the Corporation  defaults in the payment thereof. If any
date fixed for  redemption  of Series X Preferred  Stock is not a Business  Day,
then payment of the  redemption  price  payable on such date will be made on the
next  succeeding  day that is a Business  Day (and without any interest or other
payment in respect of any such delay) except that, if such Business Day falls in
the next calendar year, such payment will be made on the  immediately  preceding
Business  Day,  in each case with the same  force and  effect as if made on such
date fixed for  redemption.  If payment of the Series X Redemption  Price or any
accumulated or unpaid  distributions  in respect of the Series X Preferred Stock
is improperly withheld or refused and not paid by the Corporation, distributions
on such Series X Preferred  Stock will continue to accumulate  from the original
redemption  date to the date of payment,  in which case the actual  payment date
will be considered the date fixed for redemption for purposes of calculating the
applicable Series X Redemption Price.

        (d) Status of Redeemed Stock. Any Series X Preferred Stock that shall at
any time have been  redeemed  shall  after such  redemption,  have the status of
authorized  but unissued  Preferred  Stock,  without  designation as to class or
series until such shares are once more designated as part of a particular  class
or series by the Board of Directors.

        5. Voting Rights.  (a) General.  Holders of the Series X Preferred Stock
will not have any voting rights, except as set forth below.

      (b) Right to Elect Directors.  If the Corporation shall fail to pay full
cumulative  dividends  on the shares of Series X  Preferred  Stock or any of its
preferred  shares for six quarterly  dividend  payment  periods,  whether or not
consecutive (a "Dividend  Default"),  the holders of all  outstanding  preferred
shares,  voting as a single class without regard to series,  will be entitled to
elect two  Directors  until  full  cumulative  dividends  for all past  dividend
payment  periods on all  preferred  shares have been paid or declared  and funds
therefor  set apart for  payment.  Such right to vote  separately  as a class to
elect Directors shall, when vested,  be subject,  always, to the same provisions
for the vesting of such right to elect  Directors  separately  as a class in the
case of future Dividend Defaults. At any time when such right to elect Directors
separately as a class shall have so vested,  the Corporation may call, and, upon
the  written  request of the holders of record of not less than 20% of the total
number of preferred  shares of the Corporation then  outstanding,  shall call, a
special  meeting of stockholders  for the election of Directors.  In the case of
such a written request,  such special meeting shall be held within 90 days after
the  delivery of such  request  and, in either  case,  at the place and upon the
notice provided by law and in the Bylaws of the  Corporation;  provided that the
Corporation shall not be required to call such a special meeting if such request
is received less than 120 days before the date fixed for the next ensuing Annual
Meeting of  Shareholders  of the  Corporation  and the holders of all classes of
outstanding  preferred  shares  are  afforded  the  opportunity  to  elect  such
Directors  (or  fill  any  vacancy)  at such  Annual  Meeting  of  Shareholders.
Directors  elected as  aforesaid  shall serve  until the next Annual  Meeting of
Shareholders of the Corporation or until their  respective  successors  shall be
elected and qualified.  If, prior to the end of the term of any Director elected
as aforesaid,  a vacancy in the office of such  Director  shall occur during the
continuance  of  a  Dividend  Default  by  reason  of  death,  resignation,   or
disability,  such  vacancy  shall  be  filled  for  the  unexpired  term  by the
appointment  of a new Director for the unexpired  term of such former  Director,
such appointment to be made by the remaining Director elected as aforesaid.

        (c) Certain  Voting Rights.  So long as any Series X Preferred  Stock or
Series X Preferred  Units  exchangeable  into Series X  Preferred  Stock  remain
outstanding,  the Corporation  shall not,  without the  affirmative  vote of the
holders of a majority of the Series X Preferred  Stock  outstanding  at the time
(i)  designate or create,  or increase the  authorized  or issued amount of, any
class or series of shares  ranking  prior to the Series X  Preferred  Stock with
respect to payment of distributions or rights upon  liquidation,  dissolution or
winding-up or reclassify any authorized  shares of the Corporation into any such
shares,  or create,  authorize or issue any obligations or security  convertible
into or  evidencing  the right to purchase  any such shares,  (ii)  designate or
create,  or increase the  authorized or issued  amount of, any Parity  Preferred
Stock or  reclassify  any  authorized  shares of the  Corporation  into any such
shares,  or create,  authorize or issue any obligations or security  convertible
into or evidencing the right to purchase any such shares, but only to the extent
such Parity  Preferred  Stock is issued to an  Affiliate of the  Corporation  on
terms that differ  from the terms of any Parity  Preferred  Stock  issued to the
public or  non-Affiliates  of the Corporation,  or (iii) either (A) consolidate,
merge into or with, or convey,  transfer or lease its assets substantially as an
entirety,  to any corporation or other entity, or (B) amend, alter or repeal the
provisions  of  the  Corporation's   Charter   (including  this  Certificate  of
Determination)  or By-laws,  whether by merger,  consolidation or otherwise,  in
each case that would materially and adversely affect the powers, special rights,
preferences,  privileges or voting power of the Series X Preferred  Stock or the
holders  thereof;  provided,  however,  that with respect to the occurrence of a
merger,  consolidation or a sale or lease of all of the Corporation's  assets as
an entirety,  so long as (a) the  Corporation  is the  surviving  entity and the
Series X Preferred Stock remains  outstanding with the terms thereof  unchanged,
or (b) the resulting,  surviving or transferee entity is a corporation organized
under the laws of any state and  substitutes  the Series X  Preferred  Stock for
other preferred stock having substantially the same terms and same rights as the
Series X Preferred Stock, including with respect to distributions, voting rights
and rights upon liquidation,  dissolution or winding-up,  then the occurrence of
any such event  shall not be deemed to  materially  and  adversely  affect  such
rights,  privileges  or voting  powers of the  holders of the Series X Preferred
Stock;  and  provided,  further,  that any increase in the amount of  authorized
Preferred  Stock or the  creation  or  issuance  of any other class or series of
Preferred Stock, or any increase in an amount of authorized shares of each class
or series,  in each case  ranking  either  (a) junior to the Series X  Preferred
Stock with respect to payment of  distributions  and the  distribution of assets
upon liquidation,  dissolution or winding-up, or (b) on a parity with the Series
X Preferred Stock with respect to payment of  distributions  or the distribution
of assets  upon  liquidation,  dissolution  or  winding-up  to the  extent  such
Preferred  Stock is not issued to an Affiliate of the  Corporation on terms that
differ  from the terms of any  Parity  Preferred  Stock  issued to the public or
non-Affiliates  of the  Corporation,  shall  not be  deemed  to  materially  and
adversely affect such rights, preferences, privileges or voting powers.

        The  affirmative  vote or consent of the  holders of at least 66 2/3% of
the outstanding  shares of this Series and any other series of preferred  shares
ranking  on a parity  with this  Series as to  dividends  and upon  liquidation,
voting as a single class  without  regard to series,  will be required to issue,
authorize  or increase  the  authorized  amount of any class or series of shares
ranking prior to this Series as to dividends or upon  liquidation or to issue or
authorize any obligation or security  convertible  into or evidencing a right to
purchase any such security, but subject to Section 5(c)(ii) hereof, the Articles
of Incorporation  may be amended to increase the number of authorized  preferred
shares  ranking on a parity with or junior to this  Series or to create  another
class of  preferred  shares  ranking on a parity  with or junior to this  Series
without the vote of the holders of outstanding shares of this Series.

        6.  Conversion.  The holders of the Series X  Preferred  Stock shall not
have any rights to convert  such shares into shares of any other class or series
of stock or into any other securities of, or interest in, the Corporation.

        7. No  Sinking  Fund.  No  sinking  fund  shall be  established  for the
retirement or redemption of Series X Preferred Stock.

        8. No Preemptive  Rights.  No holder of the Series X Preferred  Stock of
the Corporation shall, as such holder, have any preemptive rights to purchase or
subscribe  for  additional  shares  of stock  of the  Corporation  or any  other
security of the Corporation which it may issue or sell.