Exhibit 10.18

                           PURCHASE AND SALE AGREEMENT


                This Agreement is entered into as of the 2nd day of May 1997, by
and among  Watkins-Johnson  Company, a California  corporation  ("Seller"),  and
CarrAmerica  Realty  Corporation,  a Maryland  corporation  and/or  its  assigns
("Buyer") and is as follows:

                          Terms and Conditions of Sale

                1.  Sale.  Seller  agrees  to sell and  convey  to Buyer "As Is"
(defined  below),  and Buyer  agrees to purchase  from  Seller "As Is",  for the
purchase  price (set  forth  below),  approximately  14.6 net acres of raw land,
located at Trimble Road and Orchard Parkway, in San Jose,  California,  as shown
on Parcel  Map,  filed in Book 415 of Maps,  pages 40 and 41,  Parcel B in Santa
Clara County  Records,  (the  "Property") on all of the terms and conditions set
forth in this Agreement.

                2.  Purchase Price and Terms of Payment.  The Purchase Price for
the Property shall be Seventeen  Million One Hundred Seventy Thousand and no/100
Dollars ($17,170,000.00) (the "Purchase Price").

                    2.1.   Within  three (3)  business  days after  execution of
this Agreement by both parties,  Buyer shall deposit with Escrow Holder (defined
below) the amount of  $500,000  as a deposit  against  the  Purchase  Price (the
"Deposit").  Said amount shall be placed into an interest-bearing  account, with
interest for the benefit of Buyer.

                    2.3    On or before the  Closing  Date (as  defined  below),
Buyer shall  deposit with Escrow  Holder the balance of the Purchase  Price,  as
well as Buyer's share of closing costs.

                3.  Escrow and Closing.

                    3.1.   Opening of Escrow.  Within one (1) business day after
the date hereof  Buyer shall open escrow  (unless  previously  opened by Seller)
with Santa Clara Land Title, 701 Miller Street, San Jose,  California 95110 (the
"Escrow Holder"), escrow officer Linda Tugade, by the deposit of the Deposit and
a copy of this Agreement  with the Escrow Holder.  Escrow Holder shall place the
Deposit in an interest  bearing  account,  with said interest for the benefit of
Buyer.  Seller  and  Buyer  agree to  prepare  and  execute  such  joint  escrow
instructions  as may be necessary and  appropriate  to close the  transaction in
accordance with the terms of this Agreement. Should said instructions fail to be
executed as  required,  Escrow  Holder  shall be and hereby is directed to close
escrow pursuant to the terms and conditions of this Agreement.

                    3.2.   Close of Escrow. The closing of the escrow ("Close of
Escrow"),  which  shall  mean the date on which the deed  transferring  title is
recorded,  shall occur within one (1) business  day of the  satisfaction  of the
conditions  stated in  Paragraphs  5 and 6, but in no event

                                       1
<PAGE>

later than June 10, 1997 (the "Closing Date"), unless the parties mutually agree
otherwise in writing.

                    3.3.   Delivery of Seller's Documents.  On or before Closing
Date,  Seller shall  deposit with Escrow  Holder all of the  following:  (i) the
fully executed and acknowledged grant deed described in subparagraph 5.2 hereof;
(ii) Seller's  escrow  instructions  sufficient to enable Escrow Holder to close
the escrow in accordance with the terms of this Agreement,  (iii) the affidavits
described in subparagraph 5.4 hereof; and (iv) any other documents,  records, or
agreements called for hereunder that have not previously been delivered.

                    3.4.   Delivery of Buyer's Documents and Funds. On or before
Closing Date,  Buyer shall deposit with Escrow Holder all of the following:  (i)
the balance of the Purchase  Price,  as well as Buyer's share of closing  costs;
(ii) Buyer's escrow instructions sufficient to enable Escrow Holder to close the
escrow  in  accordance  with the  terms of this  Agreement;  and (iii) any other
documents,  records,  agreements,  or funds called for  hereunder  that have not
previously been delivered.

                    3.5.   Prorations. Real property taxes of the Property shall
be prorated as of the Closing Date.

                    3.6.   Closing  Costs.   Each  party  shall  pay  their  own
attorney's fees associated with the negotiation of this Agreement. Recording and
Escrow fees shall be paid by Seller.  The County  transfer  tax shall be paid by
Seller and the city transfer tax shall be paid 50% each by Buyer and Seller. All
other closing costs not specifically  allocated herein to Buyer or Seller, shall
be divided and paid 50% each by Buyer and Seller.

                    3.7    Traffic  Mitigation  Costs.  At the Close of  Escrow,
$1,000,000  of the  Purchase  Price  will be  retained  by  Escrow  Holder in an
interest-bearing   account  for  the  benefit  of  Seller  ("Traffic  Mitigation
Account") to be drawn from by Buyer for any reasonable  traffic mitigation costs
attributed  directly to the Property being developed by Buyer at a .40 FAR ratio
or less ("Traffic  Mitigation  Costs") where the Traffic Mitigation Costs exceed
$1,000,000. Buyer is to pay for the first $1,000,000 of Traffic Mitigation Costs
before drawing any money from the Traffic Mitigation Account. Traffic Mitigation
Costs shall mean any onsite and offsite  transportation roadway improvements and
traffic  impact fees  attributed  directly to the  development  of the Property.
Traffic  Mitigation  Costs for either the first  $1,000,000  or from the Traffic
Mitigation  Account  shall not  include any onsite  traffic  and  transportation
roadway  improvements.  For  purposes  of this  paragraph,  "onsite"  shall mean
improvements  to be located  exclusively  within the boundaries of the property.
All requests for any draws on the Traffic Mitigation Account by Buyer shall also
be copied to Seller.  On October 21, 1997, the remaining balance of funds in the
Traffic  Mitigation  Account along with any interest earned shall be released to
Seller  except to the  extent  Buyer can  establish  at that time from a traffic
mitigation  plan  approved  by the  City  of San  Jose  for  the  Property  that
additional Traffic Mitigation Costs eligible from the Traffic Mitigation Account
as defined above will be required.  Then a sum equal to the reasonable  estimate
by Buyer of those Traffic  Mitigation Costs not yet expended shall remain in the
Traffic  Mitigation Account for draws by Buyer, up to May 1, 1998, at which time
the remaining balance of funds in the Traffic  Mitigation Account along with any
interest earned 

                                       2
<PAGE>

thereon  shall be released to Seller.  Seller shall also have the right to audit
Buyer's  requests  for draws from the Traffic  Mitigation  Account to  determine
that: (a) Buyer has expended its first  $1,000,000 on Traffic  Mitigation  Costs
and those  expenditures  are for only Traffic  Mitigation  Costs required by the
City of San Jose related  directly to the  development of the Property;  and (b)
any draws from the Traffic  Mitigation  Account are only for legitimate  Traffic
Mitigation  Costs as defined in (a) above.  Seller shall not be responsible  for
any Traffic  Mitigation  Costs or claims for costs over and above the $1,000,000
placed in the Traffic Mitigation Account.

                4.  Title and Other Contingencies.

                    4.1.   Title to be Conveyed. Seller shall convey a fee title
interest  in the  Property,  by grant deed to Buyer at Close of Escrow,  subject
only to the Approved Exceptions (as hereinafter defined).

                    4.2.   Title Insurance.  Seller, at Seller's expense,  shall
deliver to Buyer not later than five (5)  calendar  days from the date  hereof a
preliminary  report (the  "Preliminary  Report") issued by Escrow Holder ("Title
Company") and dated no earlier than as of fifteen (15) days prior to the date of
this  Agreement,  together  with legible  copies of all  documents  constituting
exceptions to title referred to in the  Preliminary  Report.  Buyer shall have a
period of fifteen (15) days ("Acceptance Period") after Seller's delivery of the
Preliminary  Report in which to review and  approve  same.  Buyer  shall  advise
Seller  within  the  Acceptance  Period as to any  exceptions  to title that are
acceptable  to Buyer.  If Buyer  fails to give notice of any  exceptions  to the
Preliminary Report within the Acceptance Period,  this will be deemed acceptance
of the Preliminary  Report by Buyer.  Upon receipt of notice of Buyer's approval
and  objections  to title,  Seller may elect to remove any  exceptions  to title
objected to by Buyer prior to Closing Date, by giving notice to Buyer within two
(2) business days after delivery to Seller of Buyer's objections. If Seller does
not so notify Buyer  within such  period,  Buyer may elect either (i) to proceed
with the purchase  and waive its title  objections,  or (ii) to  terminate  this
Agreement and receive back any deposits made by Buyer.  All  exceptions to title
set forth in the Preliminary  Report that are approved by Buyer pursuant to this
subparagraph 4.2 shall be hereinafter  collectively referred to as the "Approved
Exceptions."

                    4.3.   Form of Title  Policy.  Upon Close of  Escrow,  Title
Company shall issue at Seller's expense a standard  coverage CLTA owner's policy
of title insurance  without extended coverage (the "Title Policy") in the amount
of the Purchase  Price,  insuring that title to the Property is vested in Buyer,
subject  only to the  Approved  Exceptions.  Buyer shall pay for the cost of any
title insurance in excess of the cost(s) of the Title Policy and the cost of all
endorsements  requested by Buyer  including  any  additional  premium  charge(s)
imposed by any title company in the event the Title Policy is not issued, unless
caused by willful default of Seller.  Notwithstanding the foregoing,  Buyer may,
in its sole discretion,  elect to obtain ALTA extended coverage,  which shall be
at Buyer's sole expense, together with such endorsements as Buyer may reasonably
require.

                    4.4.   Inspection and Feasibility. Buyer shall have from the
date of this Agreement until close of business on June 6, 1997 (the  "Inspection
Period") in which to conduct inspections and feasibility studies of the Property
which  may  include,  but  not be  limited  to,

                                       3
<PAGE>

surveyors, soils inspections,  environmental site assessment,  engineering,  and
any other physical and environmental tests and inspections which Buyer may elect
to undertake,  all at Buyer's sole cost.  Buyer shall provide Seller with a plan
outlining the  particulars  of its proposed  inspection  of the Property  ("Work
Plan").  Buyer shall not proceed with  implementing  the Work Plan without first
obtaining Seller's written approval,  which shall not be unreasonably  withheld.
If within  the  Inspection  Period,  Buyer for any  reason  determines  that the
Property is not  appropriate  for its  purposes,  Buyer shall  notify  Seller in
writing,  and escrow shall be  terminated in accordance  with  subparagraph  5.7
hereof.  Failure of written  notice of rejection of the Property by Buyer within
the Inspection  Period shall be deemed  acceptance by Buyer. For said Inspection
Period,  Seller grants Buyer and/or Buyer's nominees or consultants,  engineers,
and other agents and  contractors  the right to enter upon the  Property  during
reasonable  business hours for the purpose of conducting such  examinations  and
tests as approved in the Work Plan. Buyer shall keep the Property free and clear
of any  mechanic's  liens arising out of Buyer's  entry on the  Property.  Buyer
represents and warrants that Buyer carries not less than  $1,000,000  commercial
general liability insurance with contractual liability endorsement to cover this
Agreement  which will also cover any person  accessing  the Property for Buyer's
inspection  and  feasibility  hereunder.  Buyer shall  deliver  evidence of such
insurance coverage to Seller before any such access. Seller shall cooperate with
Buyer in  facilitating  Buyer's  investigation  at no cost to Seller,  including
obtaining   information  from  and  approvals  for  testing  from   governmental
authorities.  Buyer shall  indemnify  Seller and hold Seller  harmless  from the
negligence or willful  misconduct of Buyer or Buyer's  agents on the Property or
any damage,  loss,  claim,  lien cost or expense  including  attorneys' fees and
costs arising from the exercise by Buyer or its employees,  consultants, agents,
or  representatives  of access to the Property for  inspection  and  feasibility
under this  Agreement.  Any  inspection,  test or other study or analysis of the
Property  under this  paragraph  shall be  performed  at Buyer's  expense and in
strict  accordance  with  applicable law. Buyer agrees at its expense to restore
the Property from any damage or material alteration caused by any inspections or
tests  ordered by Buyer or its agents or  consultants.  Buyer  agrees to provide
Seller,  upon Seller's  request,  with a copy of any written  inspection or test
report or  summary  Buyer has  caused to have  done or  received  regarding  the
Property,  provided  such  material  shall be  delivered  to Seller  without any
representations or warranties from Buyer, and Seller agrees it shall not rely on
such material without the prior written consent of the party preparing same.

                    4.5.   Documents.  Upon execution of this Agreement,  unless
provided  earlier  Seller shall  provide the  following  documents to Buyer:  1.
Post-Closure Report To San Jose Fire Department Permit No. CR361012595, prepared
by C.H.A.S.E.  dated July 1995, covering Seller's neighboring property. 2. Phase
II  Investigation  dated  September 11, 1992 by  Watkins-Johnson  Environmental,
covering Seller's neighboring  property.  In addition to the above, Seller shall
make a reasonable  effort to gather documents it may have regarding the Property
and give to Buyer access at Seller's  Palo Alto offices to those  documents  for
inspection  and copying at Buyer's  expense.  These  documents  are  provided by
Seller for  informational  purposes only, and Seller makes no  representation or
warranty with respect to the truth,  accuracy or  completeness  of any matter or
information  set forth in such  documents  and only  represents  that it has not
knowingly falsified the documents.

                    4.6    Hewlett-Packard  and   Watkins-Johnson   Exchange  of
Easements  Agreement.  On or about February 8, 1994,  Seller entered into a road
extension and exchange of

                                       4
<PAGE>

easements  agreement with  Hewlett-Packard  Company, a copy of which is attached
hereto as  Exhibit A  ("Hewlett-Packard  Agreement")  whereby  Seller  agreed to
exchange easements and property interests, cooperate in the application for land
use approvals,  dedication of land to the City of San Jose, and  Hewlett-Packard
Company's payment of all costs associated with this agreement  including,  inter
alia,  improving  Orchard  Parkway along  Seller's  frontage,  costs incurred in
completing the dedications described in the Hewlett-Packard Agreement, including
engineering,  mapping and title processing  costs,  the physical  realignment of
Seller's  driveways to Orchard  Parkway and Trimble Road, and to provide in kind
and at its cost  the  paving  and  other  improvements  necessary  to match  the
existing  and  no  changed   driveway.   Seller  also  agrees  to  cooperate  in
applications to the City for the proposed land use approvals. Seller does hereby
assign  to  Buyer,  Seller's  rights  and  obligations  it has  pursuant  to the
Hewlett-Packard Agreement as it pertains to the Property, and as part of Exhibit
A hereto is providing a written statement from Hewlett-Packard acknowledging (a)
that the Hewlett-Packard  Agreement is in the form attached as Exhibit A and has
not been changed;  (b) the Hewlett-Packard  Agreement is still in full force and
effect;  and (c)  Hewlett-Packard  consents to the  assignment set forth in this
sentence.  Seller  retains  any rights and  obligations  it has  pursuant to the
Hewlett-Packard  Agreement as it pertains to contiguous property owned by Seller
and  represent  that the retained  rights are not in conflict  with or interfere
with the rights  being  assigned  to Buyer in this  subparagraph  4.6,  and will
cooperate  regarding  the  retained  rights in the  contiguous  property  so the
Hewlett-Packard Agreement can be fulfilled in all respects.

                5.  Buyer's  Conditions  to Close.  For  Buyer's  sole  benefit,
Buyer's  obligation  to  complete  the  purchase  of the  Property is subject to
satisfaction of the following conditions at or prior to the Closing Date, unless
waived by Buyer in writing:

                    5.1.   Delivery of Documents,  Etc. Seller shall have timely
performed its obligations under subparagraph 3.3 hereof.

                    5.2.   Delivery  of  Deed.   Seller  shall  have   executed,
acknowledged, and delivered into Escrow for recording and subsequent delivery to
Buyer,  a grant deed  ("Deed") to the  Property in  recordable  form in the form
attached hereto as Exhibit B, conveying  Seller's title to the Property to Buyer
subject only to the Approved Exceptions.

                    5.3.   Title Policy. Title Company shall be ready,  willing,
and able to issue the Title Policy.

                    5.4.   Affidavit.  Seller shall have  executed and delivered
to Escrow  Holder an affidavit or  affidavits  satisfying  the  requirements  of
Section  1445 of the  Internal  Revenue  Code of 1986,  as  amended,  as well as
California Revenue and Taxation Code Sections 18661, et seq.

                    5.5.   Condition of the  Property.  Except as  referenced in
paragraph  10, there shall not be any material  change in the Property  from the
end of the  Inspection  Period to the Close of Escrow  unless caused by Buyer or
its agents.

                                       5
<PAGE>

                    5.6.   Seller's Performance. Seller shall have performed all
of the other  material  terms and  conditions to be performed by Seller prior to
the Closing Date under the terms of this Agreement, including but not limited to
that Seller's representations and warranties in Paragraph 8 are true and correct
as of the Close of Escrow.

                    5.7.   Termination of Escrow. If any condition  described in
this  Paragraph 5 is not timely  satisfied (or waived by Buyer in writing) on or
prior to the Closing Date, then (i) the Escrow shall terminate  immediately upon
receipt  by Escrow  Holder of  notification  from  Buyer of the  failure of such
condition,  and Buyer and Seller  shall  share  equally  any  applicable  escrow
cancellation fees, (ii) Escrow Holder shall return all instruments and documents
deposited  into the Escrow to the  parties  depositing  the same,  (iii)  Escrow
Holder  shall return to Buyer any funds  deposited  by Buyer,  less only Buyer's
share of  applicable  escrow  cancellation  fees, if any, and (iv) neither party
shall have any further rights or obligations under this Agreement, except to the
extent that the failure of a condition also constitutes a default by Seller with
respect to any of Seller's covenants or obligations under this Agreement.

                6.  Seller's  Conditions  to Close.  For Seller's  sole benefit,
Seller's  obligation  to  complete  the  sale  of the  Property  is  subject  to
satisfaction of the following conditions at or prior to the Closing Date, unless
waived by Seller in writing:

                    6.1.   Delivery of Documents,  Etc.  Buyer shall have timely
performed its obligations under Subparagraph 3.4 hereof.

                    6.2.   Receipt of Purchase  Price.  Title Company shall have
received the Purchase Price for the Property.

                    6.3.   Buyer's  Performance.  Buyer shall have performed all
of the other terms and  conditions to be performed by Buyer prior to the Closing
under the terms of this  Agreement,  including  but not limited to that  Buyer's
representations  and  warranties  in  Paragraph 7 are true and correct as of the
Close of Escrow.

                    6.4.   Termination of Escrow. If any condition  described in
this Paragraph 6 is not timely  satisfied (or waived by Seller in writing) on or
prior to Closing Date and the Paragraph 5 conditions  have been  satisfied,  (i)
the  Escrow  shall  terminate  immediately  upon  receipt  by  Escrow  Holder of
notification  from Seller of the failure of such  condition,  (ii) Escrow Holder
shall return all  instruments  and  documents  deposited  into the Escrow to the
parties  depositing  the same,  and (iii)  neither  party shall have any further
rights or  obligations to the other under this  Agreement,  except to the extent
that a failure of a condition  also  constitutes a default by Buyer with respect
to any of Buyer's covenants or obligations under this Agreement.

                7.  Buyer's   Representations   and  Warranties.   Buyer  hereby
represents  and  warrants  to  Seller,  effective  both  as of the  date of this
Agreement and as of Close of Escrow:

                    7.1.   Buyer's Due Organization and Authorization. Buyer and
those  individuals  and  entities  signing  this  Agreement  on behalf of Buyer,
respectively  have the right,  power,  and  authority to make and perform  their
obligations under this Agreement.  The 

                                       6
<PAGE>

execution,  delivery,  and  performance  of this  Agreement does not violate any
contract,  agreement,  or  commitment to which any party  comprising  Buyer is a
party or by which any party comprising Buyer is bound.

                8.  Seller's  Representations  and  Warranties.   Seller  hereby
represents  and  warrants  to  Buyer,  effective  both  as of the  date  of this
Agreement and as of Close of Escrow:

                    8.1.   Seller's Due Organization and  Authorization.  Seller
and those  individuals and entities  signing this Agreement on behalf of Seller,
respectively  have the right,  power,  and  authority to make and perform  their
obligations under this Agreement.  The execution,  delivery,  and performance of
this  Agreement does not violate any contract,  agreement,  judicial  order,  or
commitment to which any party comprising Seller is a party or by which any party
comprising Seller is bound which affect the Property.

                    8.2.   No Litigation or  Proceeding.  Seller  represents and
warrants  that there is, to its  knowledge,  no litigation  or  governmental  or
agency investigation or governmental or agency proceeding including condemnation
pending,  nor, to the  knowledge  of Seller,  threatened  against  Seller or the
Property which would impair or adversely  affect Seller's ability to perform its
obligations under this Agreement.

                    8.3.   Documents. All documents delivered to Buyer by Seller
pursuant to this Agreement are or will be to Seller's knowledge true and correct
copies of originals,  to the extent not the originals  thereof,  and any and all
information  supplied to Buyer by Seller in accordance  with this  Agreement and
all  statements  or  representations  made by Seller  herein  are and will be to
Seller's  reasonable  knowledge  true,  complete,  and  accurate in all material
respects except as specifically qualified otherwise in this Agreement.

                    8.4.   Tax  Withholding.   Seller  is  not  subject  to  tax
withholding in connection with this transaction  under the Internal Revenue Code
or other federal or state law.

                    8.5.   Bankruptcy  or  Insolvency.  Seller  has  not  made a
general assignment for the benefit of creditors, filed any voluntary petition in
bankruptcy or suffered the filing of an  involuntary  petition by its creditors,
suffered the appointment of a receiver to take possession of  substantially  all
of  its  assets,   suffered  the  attachment  or  other   judicial   seizure  of
substantially all of its assets, admitted its inability to pay its debts as they
come  due,  or made an offer of  settlement,  extension,  or  compromise  to its
creditors generally.

                    8.6.   No Leases,  etc. To Seller's  knowledge  there are no
leases, contracts or permits that affect the Property other than those disclosed
in this Agreement.

                    8.7.   Hazardous Materials.  To Seller's knowledge there are
no  Hazardous  Materials  (as  defined  in  Paragraph  26 below)  located on the
Property in violation of applicable laws in existence.

                           The term "Seller's  knowledge" or similar phrases, as
used in this Agreement, shall refer to the actual, present knowledge of David M.
Burnham,  Director of Treasury and

                                       7
<PAGE>

Corporate Real Estate for Seller,  as of the date of this Agreement  without any
duty of investigation or inquiry of any kind or nature whatsoever.

                    Buyer agrees that if, at any time prior to the Closing Date,
it has knowledge of any information which would require the qualification of any
of the above representations and warranties for such representation and warranty
to be trued, it shall immediately  notify Seller in writing of such information.
If Buyer has knowledge of the  incorrectness of any  representation  or warranty
made by Seller in the Agreement  prior to Close of Escrow and fails to so notify
Seller prior to the Closing Date, then such  representation or warranty shall be
deemed to be stricken  from this  Agreement ab initio and shall be of no further
force or effect. Seller shall have the right to qualify such representations and
warranties with any information it receives concerning such  representations and
warranties after the date of this Agreement;  but if it does so then Buyer shall
have three (3) business days from such notice to elect to either  terminate this
Agreement and the Escrow pursuant to subparagraph 5.7 herein or agree to proceed
with  the  Close of  Escrow,  in  which  event  the  above  representations  and
warranties shall be qualified as noticed by Seller.  In the event Buyer fails to
give notice of its election within the three (3) business day period, then Buyer
will be deemed to have elected to terminate this Agreement.

                9.  Indemnity.  Each party hereby agrees to  indemnify,  defend,
and hold the other party harmless from and against any and all claims,  demands,
liabilities,  costs, expenses, damages, and loss (including, without limitation,
attorneys'  fees and  costs)  resulting  from any  misrepresentation,  breach of
warranty,  or breach of  covenant  made by such  party in this  Agreement.  This
indemnity  shall  continue in effect and survive Close of Escrow,  the waiver of
any  conditions to Closing set forth herein,  and the conveyance and delivery of
title,  or, if title is not transferred  pursuant to this Agreement,  beyond any
termination of this Agreement, except as otherwise provided in Paragraph 12.

                10. Risk of Loss. The parties agree in the event that,  prior to
Closing,  any  improvements  located on the Property,  or any part thereof,  are
destroyed or materially  damaged,  the transaction  shall go forward without any
adjustment to the Purchase  Price,  but Buyer shall be entitled to any available
insurance  proceeds  resulting from such damage or destruction.  If there is any
material condemnation or threatened  condemnation of the property prior to Close
of Escrow, either party may terminate the Agreement, and it will so terminate as
set forth in paragraph 5.7.

                11. Possession.  Seller shall deliver possession of the Property
to  Buyer,  free and  clear of any  tenancies  or  contracts  or rights of third
parties not previously  approved in writing by Buyer as a part of this Agreement
such as Paragraph 4.6, as well as cleared of all equipment, vehicles, materials,
and other personal property, upon Close of Escrow.

                12. Default. In the event that the sale of the Property fails to
close as a result of a default of Seller,  Buyer may, as its sole and  exclusive
remedy,  elect to either:  (a) enforce the terms of this Agreement by action for
specific  performance,  but with no reduction in the Purchase  Price;  provided,
however, that no action for specific performance shall compel Seller to commence
litigation or cure or deal with any matters outside of its reasonable control or
expend funds as to such matters; or (b) terminate this Agreement, in which event
the Deposit  shall be returned to Buyer,  and the parties shall be released from
all further  obligations and liability under

                                       8
<PAGE>

this  Agreement  except as otherwise  specifically  provided in this  Agreement.
Under no  circumstances  of any nature  whatsoever shall Buyer have any right to
collect damages,  whether actual,  punitive,  consequential  or otherwise,  from
Seller under this Agreement. In the event that the sale of the Property fails to
close as a result of a  default  by  Buyer,  Seller's  sole  remedy  (except  as
otherwise  specifically provided hereunder) shall be to declare a forfeiture and
retain the Deposit and all interest  earned  thereon as liquidated  damages,  it
being  understood  that Seller's actual damages in the event of such default are
difficult to  ascertain  and that such  proceeds  represent  the  parties'  best
current  estimate of such damages.  Pending the full and final resolution of any
specific performance or other litigation or disputes instituted by Buyer, Escrow
Holder shall continue to hold the Deposit.

                13. Liquidated  Damages.  BY PLACING THEIR INITIALS  IMMEDIATELY
BELOW,  BUYER AND  SELLER  AGREE  THAT IT WOULD BE  IMPRACTICABLE  OR  EXTREMELY
DIFFICULT TO FIX ACTUAL DAMAGES IN THE EVENT OF A DEFAULT BY BUYER, THAT THE SUM
OF BUYER'S INITIAL AND ADDITIONAL  DEPOSITS IS THE PARTIES'  REASONABLE ESTIMATE
OF SELLER'S DAMAGES IN THE EVENT OF BUYER'S DEFAULT, AND THAT IN THE EVENT BUYER
FAILS TO TIMELY  PURCHASE  THE  PROPERTY  IN  ACCORDANCE  WITH THE TERMS OF THIS
AGREEMENT  BECAUSE  OF A DEFAULT BY BUYER,  SELLER  SHALL BE  RELEASED  FROM ITS
OBLIGATION TO SELL THE PROPERTY, AND, AT SELLER'S SOLE ELECTION, SELLER SHALL BE
ENTITLED TO RETAIN  BUYER'S  INITIAL AND  ADDITIONAL  DEPOSITS  AND ALL INTEREST
EARNED THEREON AS LIQUIDATED DAMAGES.

                SELLER'S INITIALS /s/SGB     BUYER'S INITIALS /s/RGS

                14. No  Commissions.  Except  as to Mark T.  Ziemendorf  and Rod
Shepard, of Cornish & Carey Commercial,  Santa Clara,  California,  representing
both Buyer and Seller,  whose commission  (collectively)  in the amount of three
percent (3%) of the Purchase  Price  Seller  agrees to pay at its cost,  neither
party  has  had  any  contact  or  dealings  regarding  the  Property,   or  any
communication in connection with the subject matter of this transaction, through
any  licensed  real  estate  broker or other  person  who can claim a right to a
commission or finder's fee as a procuring cause of the sale contemplated herein.
In the event that any broker or finder  perfects a claim for a  commission  or a
finder's fee based upon any  contract,  dealings,  or  communication,  the party
through whom the broker or finder makes his claim shall be responsible  for said
commission  or fee and  shall  indemnify  and hold  harmless  as to all  claims,
liabilities,  costs, and expenses (including without limitation as to attorneys'
fees and court  costs)  suffered or  incurred  by the other  party in  defending
against same.

                15. Assignment. This Agreement shall inure to the benefit of and
be binding upon the parties hereto and their respective  successors and assigns.
Notwithstanding  the foregoing,  neither party may assign this Agreement without
the other party's prior written consent,  except Seller hereby consents to Buyer
assigning this Agreement to a related entity such as a Buyer managed LLC.

                                       9
<PAGE>

                16. Attorneys'  Fees.  In the event either party hereto fails to
perform any of its  obligations  under this  Agreement or in the event a dispute
arises  concerning  the  meaning  or  interpretation  of any  provision  of this
Agreement,  the defaulting party or the party not prevailing in such dispute, as
the case may be, shall pay any and all costs and expenses  incurred by the other
party in enforcing or  establishing  its rights  hereunder,  including,  without
limitation, court costs and attorneys' fees.

                17. Time.  Time is of the essence of this  Agreement  as to each
and every provision hereof.

                18. Notices.  All  notices or other  communications  to be given
hereunder  shall be in  writing  and shall be deemed  received  when  personally
delivered by commercial  courier  including an overnight courier such as Federal
Express,  or upon confirmation of receipt when given by telecopy or facsimile to
the address and facsimile  number(s) set forth below, or three (3) business days
after deposit in the United States  certified  mail,  return receipt  requested,
postage prepaid, addressed as follows:

                If to Seller:

                Watkins-Johnson Company
                Stanford Research Park
                3333 Hillview Avenue
                Palo Alto, CA  94304-1223
                Attn:  David M. Burnham
                Tel:  (415) 813-2990
                Fax:  (415) 813-2545

                Copy to:

                Garth E. Pickett, Esq.
                Hopkins & Carley, A Law Corporation
                Ten Almaden Boulevard, Eighth Floor
                San Jose, CA  95113-2228
                Tel:  (408) 286-9800
                Fax:  (408) 998-4790

                If to Buyer:

                Hunter Barrier
                CarrAmerica Realty Corporation
                1700 Pennsylvania Avenue, NW
                Washington, DC  20006
                Tel:  (202) 639-3867
                Fax:  (202) 737-2147

                                       10
<PAGE>

                Copy to:

                Caroline Brower
                Mayer, Brown & Platt
                141 East Palace Avenue
                Santa Fe, NM  87501
                Tel:  (505) 820-8186
                Fax:  (505) 820-7334

Any party may change its  address for the  purpose of this  paragraph  by giving
written notice of such change to the other party in the manner herein provided.

                19. Entire   Agreement.  This  Agreement  expresses  the  entire
agreement of the parties and supersedes any and all previous  agreements between
the parties with regard to the Property. There are no other understandings, oral
or  written,  which in any way  alter or  enlarge  its  terms,  and there are no
warranties  or  representations  of any  nature  whatsoever,  either  express or
implied,  except as set forth herein. Any future  modification of this Agreement
will be  effective  only if it is in  writing  and  signed  by the  party  to be
charged.

                20. Governing   Law.  This  Agreement  shall be  governed by and
construed in accordance with the laws of the State of California.

                21. Waiver.  The   waiver  by  either  party of a breach  of any
provision of this Agreement shall not be deemed a continuing  waiver or a waiver
of any subsequent breach, whether of a like nature or otherwise.

                22. Counterparts.   This    Agreement   may   be   executed   in
counterparts,  each of  which  shall  be  deemed  to be an  original,  but  such
counterparts together shall constitute only one agreement.

                23. Headings. The Paragraph and Subparagraph headings throughout
this Agreement are for  convenience  and reference only, and the words contained
therein  shall  not  be  held  to  expand,   modify,   amplify  or  aid  in  the
interpretation, construction or meaning of this Agreement.

                24. Survival.   All   representations  and   warranties  by  the
respective  parties  contained  herein  or  made  in  writing  pursuant  to this
Agreement  are  intended to and shall remain true and correct as of the Closing,
shall be deemed  material and shall  survive the  execution and delivery of this
Agreement,  the  Closing,  the  delivery  of the Grant Deed and the  transfer of
title,  or, if title is not transferred  pursuant to this Agreement,  beyond any
termination of this Agreement.

                25. Further Assurances. Each party hereto agrees to execute such
other  documents or  instruments  as are necessary or  appropriate to effectuate
this Agreement and  consummate the  transaction  provided  herein  promptly upon
request therefor.

                                       11
<PAGE>

                26. "As Is" Clause. EXCEPT AS TO THOSE SPECIFIC  REPRESENTATIONS
AND WARRANTIES BY SELLER IN THIS AGREEMENT, BUYER SPECIFICALLY ACKNOWLEDGES THAT
SELLER IS SELLING  AND BUYER IS  PURCHASING  THE  PROPERTY ON AN "AS IS WITH ALL
FAULTS" BASIS AND THAT BUYER IS NOT RELYING ON ANY REPRESENTATIONS OR WARRANTIES
OF ANY KIND WHATSOEVER,  EXPRESS OR IMPLIED, FROM SELLER, ITS AGENTS, OR BROKERS
AS TO ANY MATTERS CONCERNING THE PROPERTY, INCLUDING WITHOUT LIMITATION: (i) the
quality,  nature,  adequacy, and physical condition of the Property,  including,
but not limited to, the quality,  nature,  adequacy,  and physical  condition of
soils,  geology  and any  groundwater,  (ii)  the  existence,  quality,  nature,
adequacy,  and physical  condition of utilities serving the Property,  (iii) the
development  potential of the Property,  and the Property's  use,  habitability,
merchantability,  or fitness, suitability, value or adequacy of the Property for
any particular purpose, (iv) the zoning or other legal status of the Property or
any  other  public  or  private  restrictions  on use of the  Property,  (v) the
compliance of the Property or its operation  with any  applicable  codes,  laws,
regulations, statutes, ordinances, covenants, conditions and restrictions of any
governmental or quasi-governmental entity or of any other person or entity, (vi)
the  presence or removal of Hazardous  Materials  under or about the Property or
the adjoining or neighboring  property;  and (vii) the condition of title to the
Property.  The term  "Hazardous  Materials"  shall mean any  hazardous  or toxic
materials,  substances  or wastes,  such as (A) those  materials  identified  in
Sections 66680 through 66685 and Sections 66693 through 66740 of Title 22 of the
California  Administrative Code, Division 4, Chapter 30, as amended from time to
time, (B) those materials  defined in Section  255010) of the California  Health
and  Safety  Code,  (C) any  materials,  substances  or wastes  which are toxic,
ignitable,   corrosive  or  reactive  and  which  are  regulated  by  any  local
governmental  authority,  any agency of the state of California or any agency of
the United States  Government,  (D) asbestos,  (E) petroleum and petroleum based
products, (F) urea formaldehyde foam insulation,  (G) polychlorinated  biphenyls
(PCBs), and (H) freon and other chlorofluorocarbons.

                27. Condition  of Property.  Buyer  acknowledges and understands
that Seller's  Broker has disclosed that the Property may be situated within (i)
an Earthquake  Fault Zone as so designated under the  Alquist-Priolo  Earthquake
Fault Zoning Act, Section 2621 et. seq. of the California Public Resources Code;
and/or (ii) a Seismic  Hazards Zone as so designated  under the Seismic  Hazards
Mapping  Act,  Section 2690 et. seq. of the  California  Public  Resources  Code
(collectively  herein referred to as the "Seismic Disclosure Acts"); and (iii) a
100 year flood zone or  potentially  other  special  flood  hazard  area.  Buyer
acknowledged  that  it has had  delivered  by  Seller's  agents  the  Commercial
Property  Owner's  Guide  to  Earthquake  Safety,  published  by  the  State  of
California Seismic Safety  Commission.  Buyer hereby waives any seismic or flood
zone disclosure requirements imposed on Seller by California law.

                28. Approval.  Upon Buyer's execution of this Agreement,  Seller
shall have two (2) business days in which to approve this Agreement.  Failure of
timely  delivery  of an  executed  agreement  by Seller to Buyer shall be deemed
rejection  and Buyer's  offer will be deemed  withdrawn  as of the  rejection by
Seller if so elected by Buyer within two (2) business days thereafter.

                Executed as of the date first set forth above.


                                       12
<PAGE>

"BUYER"                                                "SELLER"

CARRAMERICA REALTY,                                    WATKINS-JOHNSON COMPANY,
CORPORATION                                            a California corporation
a Maryland corporation



By: /s/ Robert G. Stuckey                              By: /s/ Scott G. Buchanan
Its: Managing Director                                 Its: Vice President & CFO



                     FIRST AMENDMENT TO AND REAFFIRMATION OF
                           PURCHASE AND SALE AGREEMENT


         This First Amendment to and Reaffirmation of Purchase Agreement ("First
Amendment")  is made  as of  August  15,  1997  by and  between  Watkins-Johnson
Company,   a  California   corporation   ("Seller"),   and  CarrAmerica   Realty
Corporation, a Maryland corporation ("Buyer").

                                    RECITALS

         A. Seller and Buyer have previously  entered into that certain Purchase
and  Sale  Agreement  dated  as of the 2nd day of May  1997  (the  "Agreement").
Capitalized  items not otherwise  defined herein shall have the meaning assigned
to them in the Agreement.

         B.  Seller  and  Buyer  hereby   acknowledge  that  the  Agreement  was
terminated at the end of the  Inspection  Period by Buyer.  Notwithstanding  the
foregoing,  Buyer and Seller  hereby elect to revive and reaffirm the  Agreement
and all the terms  thereof,  and to amend the  Agreement  in  certain  respects,
including to: (i) clarify the  description  of the Property;  (ii)  establish an
additional  contingency  related to receiving a Site Development  Permit;  (iii)
extend the date for close of escrow; (iv) revise the amount of the Deposit;  (v)
give Seller the right to participate in the Site Development  Permit Application
and to take over such  Application  process in the event  Buyer  terminates  the
Agreement;  and (vi) Buyer grant to Seller a certain  easement to be recorded at
close of escrow, all as hereinafter provided.

                                    AGREEMENT

         NOW, THEREFORE,  in consideration of the foregoing recitals, the mutual
covenants  and  agreements  contained in this  agreement  and for other good and
valuable  consideration,  the  receipt  and  sufficiency  of  which  are  hereby
acknowledged, Seller and Buyer hereby agree to amend the Agreement as follows:

                                       13
<PAGE>

         1.     Reaffirmation  of Agreement.  Seller and Buyer hereby agree that
not withstanding anything to the contrary contained in the Agreement,  effective
as of the date  hereof,  the  Agreement  shall be in full  force and  effect and
Seller and Buyer hereby  reaffirm the  Agreement  in  accordance  with its terms
except as amended by this First Amendment.

         2.     The  Property  is more  particularly  described  in Exhibit  "A"
attached hereto.

         3.     Deposit.  The  Deposit  as set  forth  in  Paragraph  2.1 of the
Agreement  shall be $1,000,000  with any additional  sums necessary to bring the
Deposit  to  $1,000,000  to be  deposited  with the  escrow  holder  by close of
business on the third (3rd) business day after the date of this First Amendment.
The  Deposit may be  increased  or  decreased  by (Delay  Damages) as  hereafter
defined  prior to close of escrow as set forth in  Paragraph  5  hereafter.  All
reference in the  Agreement  and this First  Amendment to the Deposit shall mean
and refer to the amount of  $1,000,000  as may be changed  pursuant to Paragraph
6(b) hereafter.

         4.     Escrow and Closing:

                (a) Closing  Date.  Paragraph 3.2 of the Agreement is amended to
change the  Closing  Date to three (3)  business  days  after  receipt of a Site
Development  Permit Approval from the City of San Jose or Buyer's waiver of this
contingency,  but in no event later than  October  21, 1997 unless the  Approval
Date is  extended  pursuant  to  Paragraph  6(b) below.  All  references  in the
Agreement to the Closing Date shall mean the above.

                (b)  Traffic  Mitigation  Costs.  The  October  21, 1997 date in
Paragraph  3.7 of the  Agreement  is changed to the  earlier of thirty (30) days
after the "Approval" as  hereinafter  defined or March 15, 1998. The May 1, 1998
date in Paragraph 3.7 of this Agreement is changed to August 3, 1998.

         5.     Title Insurance and Inspection Period. Buyer hereby acknowledges
that the  Preliminary  Report  dated July 14,  1997 is  acceptable  and that the
Acceptance Period has expired,  and that the Inspection Period is deemed to have
expired and all inspections satisfied.  The Approved Exceptions are those listed
in Exhibit "B" attached  hereto.  The issuance of the ALTA title policy pursuant
to  Paragraph  4.3 of the  Agreement  is a  condition  to the  Closing  with the
endorsements  identified in Exhibit "C" attached hereto. At the Closing,  Seller
shall execute a standard  affidavit or  declaration  that Seller has not done or
caused to be done any work of  improvement  on the Property  that could create a
mechanic's  lien(s) and has been in possession of the Property with no leases or
right of  possession  having  been given to any other  party as set forth in the
Approved  Exceptions.  A new  contingency  shall be  established  regarding  the
approval  of a "Site  Development  Permit  Application"  by the City of San Jose
Planning Department (the "City") as set forth below.

         6.     Site Development Permit Contingency.  Section 4 of the Agreement
shall be amended to add as a contingency the City granting  approval of the Site
Development  Permit Application as set forth herein  ("Approval").  The Approval
shall mean the granting of the Site Development  Permit,  subject to the minimum
acceptable requirements as set forth in Paragraph 6(b) below (the "Permit") plus
the running of any  applicable  appeal period for appealing to the City Council.
The terms of this contingency are more particularly as follows:

                                       14
<PAGE>

                (a) Site Development Permit  Application.  Buyer shall submit to
the City a  substantially  complete Site  Development  Permit  Application  (the
"Substantial  Application")  for the  Property  no later than  August  15,  1997
("Permit Application Date"). A substantially complete application means one that
includes the  completed  City  application  form, a Traffic  Study and Site Plan
architectural  drawings.  Buyer  shall  submit  to  the  City  a  complete  Site
Development  Permit  Application (the  "Application")  for the Property no later
than August 22, 1997 ("2nd Permit  Application  Date").  A complete  Application
means  one  that is  intended  to  include  all  submittal  items  that the City
requires,  although the City may require  further  submittals.  The  Application
shall  be a joint  application  on  behalf  of the  Buyer as the  purchaser  and
developer and Seller as the owner of the property.  Seller will  cooperate  with
submitting  the  Application  as  reasonably  requested  by  Buyer at no cost to
Seller.  In the event Buyer fails to submit the  Substantial  Application by the
Permit  Application  Date and/or the  Application by the 2nd Permit  Application
Date,  Seller  shall be  entitled to withdraw  from  escrow  $100,000.00  of the
Deposit as liquidated  damages for such delay in filing the Application by Buyer
("Delay  Damages"),  unless  Buyer  establishes  that the  delay is  beyond  the
reasonable  control of Buyer and  through no fault of Buyer.  The payment of the
Delay Damages  shall be applicable to the Purchase  Price and Buyer shall not be
required to replace it in the Deposit.  If Buyer fails to submit the Substantial
Application  by the Permit  Application  Date and/or the  Application by the 2nd
Permit  Application  Date,  Seller shall either  terminate the Agreement and the
Deposit less the Delay Damages shall be released to Buyer,  or be deemed to have
extended  (after  payment  of the Delay  Damages,  if  applicable),  the  Permit
Application Date to August 29, 1997 ("Extended Permit Application Date"). If the
Application is not filed by the Extended Permit  Application Date, the Agreement
is deemed  terminated and the Deposit less the Delay Damages if applicable  will
be returned to Buyer.

                (b) Approval ("Approval Date") of Application.  Buyer shall have
until October 15, 1997 in which to receive the Approval  ("Approval  Date").  If
Approval  from the City is not  received by the Approval  Date,  Buyer shall (i)
waive in writing the Approval  contingency;  or (ii) extend the Approval Date to
December  15,  1997  ("Extended  Approval  Date")  upon  placing  into escrow an
additional $250,000 to be added to the Deposit.  Thereafter,  Deposit shall mean
$1,250,000 less the Delay Damages, if applicable. If Approval is not received by
the  Extended  Approval  Date,  Buyer  shall (i) waive in writing  the  Approval
contingency,  or (ii) extend the Approval  Date to February 15, 1998 (the "Final
Approval Date") upon placing an additional  $250,000 into escrow and the Deposit
shall  mean  $1,500,000  less the Delay  Damages,  if  applicable.  If the Final
Approval Date is reached,  or Buyer fails to extend the Approval Date as allowed
above  and  Buyer  has  not in  either  case  waived  in  writing  the  Approval
contingency,  the Buyer will be deemed in default, the Agreement shall terminate
and  Seller  will be  entitled  to the  entire  Deposit  in escrow  pursuant  to
Paragraph 13 of the Agreement.  The Approval  Contingency shall be met if, on or
before the Final  Approval  Date,  the City  approves  the  Application  and the
supporting  plans,  studies and other  components of the  Application.  Approval
includes all  administrative  action  required to make such  approval  final and
binding  under  applicable  law.  Buyer may by written  notice to Seller and the
Escrow Agent  terminate the Agreement and receive a refund of the Deposit if any
of the following occurs prior to the Final Approval Date:

                                       15
<PAGE>

                    (i)  the City  requires  a  project  specific  environmental
impact report ("EIR"),  or the City delays approval pending the preparation of a
new or updated EIR for the Rincon De Los Estros Redevelopment area by either the
City or some other party or entity; or

                    (ii) the  City  denies  the  Application   substantially  as
submitted by Buyer.

                The  City  shall  be  deemed  to  have  denied  the  Application
substantially  submitted  by  Buyer  thereby  allowing  Buyer to  terminate  the
Agreement and receive a refund of the Deposit,  less Delay  Damages,  if any, if
the approval requires any of the following:

                         (1) Traffic  Mitigation  Costs, as defined in Paragraph
3.7  of  the  Agreement   that  exceeds  $3  million  in  the   aggregate,   and
Watkins-Johnson  has not  agreed,  in writing,  to cover any Traffic  Mitigation
Costs in excess of $3 million in the aggregate;

                         (2) Failure to give fully permitted  ingress and egress
access to either Trimble Road or Orchard Parkway from the Property;

                         (3) An FAR  that is less  than  the  smaller  of 0.4 or
Buyer's   submittal  of  FAR  in  the   Application   for  less  than  0.4,  and
Watkins-Johnson  does not agree, in writing, to reduce the purchase price by the
same percentage that the approved FAR is below the above standard.  For example,
if the submitted  FAR is a 0.4 and the approved FAR is a 0.35,  this is a 12-1/2
percent  reduction  which would be a 12-1/2  percent  reduction  in the Purchase
Price by Watkins-Johnson for this contingency to be met. Buyer may terminate the
Agreement and receive a refund of the Deposit less Delay Damages, if applicable,
if the  approval  requires a FAR less than 0.35.  Buyer  shall not submit in the
Application for an FAR greater than 0.4.

                (c) Buyer's Diligent Efforts During  Application  Period.  Buyer
shall diligently, adequately, timely, and in good faith respond to inquiries and
requests  from  the  City  during  the  approval  process  for  the  Application
("Standard of Conduct").  However,  Buyer may reasonably  object to City imposed
requirements,  conditions or restrictions  and negotiate with the City to secure
favorable approval terms. If Buyer does not meet this Standard of Conduct and as
a result the City  denies the  Application,  then  Seller  shall be  entitled to
retain the Deposit.

                (d) Seller's Rights Upon Termination to the  Application.  Buyer
hereby  covenants  and agrees to  cooperate in the event Buyer  terminates  this
Agreement pursuant to Paragraph 6(b) above by assigning to Seller all of Buyer's
rights and interest in the Application,  and to furnish to Seller, at no cost to
Seller,  copies of the  traffic  studies and any other  studies and  information
compiled by Seller in  preparation of the  Application or any other  information
requested by the City pursuant to the  Application  and to turn such over to the
Seller for its use in continuing  to pursue the  Application  in Seller's  name.
Buyer  agrees at no  additional  cost to Buyer to  cooperate  with Seller in the
transfer  of Buyer's  rights and  obligations  in the  Application  to Seller as
reasonably requested by Seller.

                                       16
<PAGE>

         7.     Grant of Easement By Buyer To Seller: Section 6 of the Agreement
is amended to add the following:

                6.5.     Grant Of Easement. Buyer hereby agrees and covenants to
         grant, at the close of escrow,  to Seller for the benefit of Parcel A a
         non-exclusive  easement for ingress and egress along the roadway  being
         conveyed to Buyer as the Property's  access to Component  Drive, and in
         the form and description as attached hereto as Exhibit C.


         8.     Miscellaneous.

                (a) Effect  of  First  Amendment.   Except  to  the  extent  the
Agreement  is  modified  by  this  First  Amendment,  the  remaining  terms  and
conditions  of the  Agreement  shall  remain  unmodified  and in full  force and
effect.  In the  event of  conflict  between  the terms  and  conditions  of the
Agreement and the terms and  conditions of this First  Amendment,  the terms and
conditions of the First Amendment shall prevail and control.

                (b) Entire  Agreement.  The Agreement,  together with this First
Amendment,  embodies  the  entire  understanding  between  Seller and Buyer with
respect  to its  subject  matter  and  supersedes  all other  prior  agreements,
representations and covenants, written or oral, with respect thereto; and can be
changed only by an instrument in writing signed by Seller and Buyer.

                (c) Counterparts. This First Amendment may be executed in one or
more  counterparts,  each of which shall be deemed an original but all of which,
taken together, shall constitute one and the same amendment.

         IN WITNESS  WHEREOF,  this First  Amendment has been executed as of the
day and year first set forth above.


"BUYER"                                                 "SELLER"

CARRAMERICA REALTY,                                     WATKINS-JOHNSON COMPANY,
CORPORATION,                                            a California corporation
a Maryland corporation


By: /s/ Robert G. Stuckey                               By: /s/ W. Keith Kennedy
Its: Managing Director                                  Its: President & CEO

                                       17