Document:

<PAGE>

                                                             EXECUTION VERSION

                               SECOND AMENDMENT TO
                      AMENDED AND RESTATED CREDIT AGREEMENT

         THIS SECOND AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT (this
"AMENDMENT"), dated as of January 28, 2000, is entered into by and among:

                  (1) ADAC LABORATORIES, a California corporation
         ("BORROWER");

                  (2) Each of the financial institutions listed in SCHEDULE I
         TO THE CREDIT AGREEMENT referred to in RECITAL A below (such
         financial institutions to be referred to herein collectively as the
         "EXISTING LENDERS");

                  (3) ABN AMRO BANK N.V., a Netherlands public company acting
         through its San Francisco Representative Office, as agent for the
         Lenders (as defined below) (in such capacity, "AGENT"); and

                  (4) COMERICA BANK - CALIFORNIA, a California banking
         corporation, that will become a party to the Credit Agreement
         pursuant to this Amendment (the "NEW LENDER", and together with the
         Existing Lenders, the "Lenders").

                                    RECITALS

         A. Borrower, the Existing Lenders and Agent are parties to an
Amended and Restated Credit Agreement dated as of March 29, 1999, as amended
by that certain First Amendment to Credit Agreement dated as of August 17,
1999 (as amended, the "CREDIT AGREEMENT"). Pursuant to the Credit Agreement,
the Existing Lenders have agreed to provide to Borrower certain credit
facilities with a Total Commitment of $75,000,000.

         B. Borrower has requested the Existing Lenders and Agent to amend
the Credit Agreement in certain respects and increase the Total Commitment to
$85,000,000.

         C. In order to facilitate the increase of the Total Commitment to
$85,000,000, Borrower has requested that the New Lender become a party to the
Credit Agreement.

         D. The New Lender is willing to become a party to the Credit
Agreement, and the New Lender, the Existing Lenders and Agent are willing to
so amend the Credit Agreement upon the terms and subject to the conditions
set forth below.

<PAGE>

                                    AGREEMENT

         NOW, THEREFORE, in consideration of the above recitals and for other
good and valuable consideration, the receipt and adequacy of which are hereby
acknowledged, Borrower, the Existing Lenders, the New Lender and Agent hereby
agree as follows:

         1. DEFINITIONS, INTERPRETATION. All capitalized terms defined above
and elsewhere in this Amendment shall be used herein as so defined. Unless
otherwise defined herein, all other capitalized terms used herein shall have
the respective meanings given to those terms in the Credit Agreement, as
amended by this Amendment. The rules of construction set forth in SECTION I
OF THE CREDIT AGREEMENT shall, to the extent not inconsistent with the terms
of this Amendment, apply to this Amendment and are hereby incorporated by
reference.

         2. ALLOCATION OF OUTSTANDING LOANS AMONG THE EXISTING LENDERS AND
THE NEW LENDER. Subject to the satisfaction of the conditions set forth in
PARAGRAPH 5 below, Borrower, the Existing Lenders, the New Lender and Agent
hereby agree that on and after the Second Amendment Effective Date (as
defined below), each Existing Lender and the New Lender shall be a Lender
under the Credit Agreement and the other Credit Documents with Proportionate
Shares as set forth on SCHEDULE I OF THE CREDIT AGREEMENT (as amended
pursuant to this Amendment), with the rights, duties and obligations of such
a Lender under the Credit Agreement and the other Credit Documents. To
effectuate the foregoing, on the Second Amendment Effective Date Agent shall
calculate the Proportionate Share of each Existing Lender and the New Lender
in each Borrowing then outstanding. Based upon such calculation, the New
Lender shall purchase from the Existing Lenders such shares in the
outstanding Loans as Agent determines is necessary to cause each Existing
Lender and the New Lender to hold Loans in each outstanding Borrowing in a
principal amount equal to such Existing Lender's and such New Lender's
Proportionate Share of such Borrowings.

         3. AMENDMENTS TO CREDIT AGREEMENT. Subject to the satisfaction of
the conditions set forth in PARAGRAPH 5 below, the Credit Agreement is hereby
amended as follows:

                  (a) PARAGRAPH 1.01 is hereby amended by adding thereto, in
         appropriate alphabetical order, definitions of the terms "Litigation
         Settlement Payment" and "Litigation Settlement Payment Non-Recurring
         Charge" to read in their entirety as follows:

                           "LITIGATION SETTLEMENT PAYMENT" shall mean an
                  amount (including related legal fees), not to exceed
                  Fifteen Million Dollars ($15,000,000),to be paid by
                  Borrower as a result of its settlement of various lawsuits
                  with certain of its shareholders, including without
                  limitation "In re ADAC Laboratories Securities Litigation,
                  Master File No. C-98-4934-MHP" and Civil Action CV779262,
                  pending in the County of Santa Clara, California.

                           "LITIGATION SETTLEMENT PAYMENT NON-RECURRING
                  CHARGE" shall mean (without duplication of amounts
                  previously charged in connection with the 1999 Litigation
                  Reserve) the non-recurring charge, not to exceed
                  $15,000,000 (pre-tax)

                                       2
<PAGE>

                  in the aggregate, to be taken by Borrower during its fiscal
                  year 2000 as a result of its payment of the Litigation
                  Settlement Payment.

                  (b) PARAGRAPH 1.01 is hereby further amended by changing
         the definition of the term "EBITDA" set forth therein to read in
         its entirety as follows:

                           "EBITDA" shall mean, with respect to Borrower and
                  its Subsidiaries for any period, the sum of the following,
                  determined on a consolidated basis in accordance with GAAP:

                                    (a) The net income of Borrower and its
                           Subsidiaries for such period before provision for
                           income taxes;

                                      PLUS

                                    (b) The sum (to the extent deducted in
                           calculating such net Income for such period under
                           CLAUSE (a) above) of (i) all Interest Expenses of
                           Borrower and its Subsidiaries accrued during such
                           period and (ii) all depreciation and amortization
                           expenses of Borrower and its Subsidiaries accrued
                           during such period;

                                      PLUS

                                    (c) To the extent deducted in calculating
                           such net income for such period under CLAUSE (a)
                           above, (i) all Acquisition In-Process R&D Charges
                           taken by Borrower and its Subsidiaries during such
                           period, (ii) all 1999 Non-Recurring and
                           Non-Ordinary Charges taken by Borrower and its
                           Subsidiaries during such period, (iii) all
                           Capitalized Spare Parts 1999 Non-Ordinary Charges
                           taken by Borrower and its Subsidiaries during such
                           period; (iv) all Latin American Notes 1999
                           Non-Ordinary Charges taken by Borrower and its
                           Subsidiaries during such period and (v) all
                           Litigation Settlement Payment Non-Recurring
                           Charges taken by Borrower and its Subsidiaries
                           during such period.

                  (c) PARAGRAPH 1.01 is hereby further amended by changing
         the definition of the term "Total Commitment" set forth therein to
         read in its entirety as follows:

                           "TOTAL COMMITMENT" shall mean, at any time, Eighty
                  Five Million Dollars ($85,000,000) or, if such amount is
                  reduced pursuant to SUBPARAGRAPH 2.02(a), the amount to
                  which so reduced and in effect at such time.

                  (d) SUBPARAGRAPH 5.02(a) is hereby amended by changing
         CLAUSE (iv) thereof to read in its entirety as follows:

                           (iv) Indebtedness of Borrower and its Subsidiaries
                  under Rate Contracts, provided that (A) all such
                  arrangements are entered into in connection with bona fide
                  hedging operations and not for speculation and (B) the
                  aggregate

                                       3
<PAGE>

                  net amount owed by Borrower and its Subsidiaries under, on
                  account of or otherwise in connection with such Rate
                  Contracts does not exceed $10,000,000 (marked to market) at
                  any time;

                  (e) SUBPARAGRAPH 5.03(b) is hereby amended by changing the
         INTRODUCTORY CLAUSE thereof to read in its entirety as follows:

                           (b) TANGIBLE NET WORTH. Borrower shall not permit
                  the sum of (1) Tangible Net Worth of Borrower and its
                  Subsidiaries on the last day of any fiscal quarter (any
                  such date to be referred to herein as a "determination
                  date") which occurs on or after July 4, 1999 (such date to
                  be referred to herein as the "base date") PLUS (2) the
                  after tax amount (if any) of the Capitalized Spare Parts
                  1999 Non-Ordinary Charges, the Latin American Notes 1999
                  Non-Ordinary Charges and the Litigation Settlement Payment
                  Non-Recurring Charges of Borrower and its Subsidiaries (as
                  applicable) for each quarter after the base date through
                  and including the quarter ending immediately prior to the
                  determination date, to be less than the sum on such
                  determination date of the following:

                  (f) SUBPARAGRAPH 5.03(c) is hereby amended to read in its
          entirety as follows:

                                    (c) DEBT/EBITDA RATIO. Borrower shall not
                           permit the Debt/EBITDA Ratio of Borrower and its
                           Subsidiaries to be greater than the ratios set
                           forth below as of the end of the four fiscal
                           quarter periods set forth below:

                                    Four fiscal quarter period ending on each
                                    of the last day of the third fiscal
                                    quarter in 1999, and the fourth fiscal
                                    quarter in 1999                3.00 to 1.00

                                    Four fiscal quarter period ending on the
                                    last day of the first fiscal quarter in
                                    2000                           3.25 to 1.00

                                    Four fiscal quarter period ending on the
                                    last day of the second fiscal quarter in
                                    2000                           3.00 to 1.00

                                    Four fiscal quarter period ending on the
                                    last day of the third fiscal quarter in
                                    2000 and the date day of each fiscal
                                    quarter thereafter            2.50 to 1.00;

                           PROVIDED, HOWEVER, that for every four fiscal
                           quarter period ending on the last day of a fiscal
                           quarter occurring after the date Agent and the
                           Lenders release their security interest in the
                           Collateral securing the Secured

                                       4
<PAGE>

                           Obligations pursuant to SUBPARAGRAPH 2.12(e),
                           Borrower shall not permit the Debt/EBITDA Ratio of
                           Borrower and its Subsidiaries to be greater than
                           2.00 to 1.00.

                  (g) SUBPARAGRAPH 5.03(d) is hereby amended to read in its
         entirety as follows:

                                    (d) PROFITABILITY. Borrower shall not
                           permit the consolidated net income of Borrower and
                           its Subsidiaries (i) for the third fiscal quarter
                           in 1999 to be a loss in excess of $9,000,000, (ii)
                           for the fourth fiscal quarter in 1999 to be less
                           than $1.00 and (iii) for any other fiscal quarter
                           to be less than $1.00. In calculating the
                           consolidated net income of Borrower and its
                           Subsidiaries for the third fiscal quarter in 1999,
                           an amount equal to the after-tax sum of any Latin
                           American Notes 1999 Non-Ordinary Charges taken by
                           Borrower during such fiscal quarter shall be
                           ignored. In addition, in calculating the
                           consolidated net income of Borrower and its
                           Subsidiaries for the fourth fiscal quarter in
                           1999, an amount equal to the sum of the 1999
                           Litigation Reserve, the after-tax sum of any
                           Capitalized Spare Parts 1999 Non-Ordinary Charges
                           and the Latin American Notes 1999 Non-Ordinary
                           Charges taken by Borrower during such fiscal
                           quarter shall be ignored. Moreover, in calculating
                           the consolidated net income of Borrower and its
                           Subsidiaries for the fiscal quarter in 2000 in
                           which Borrower records the Litigation Settlement
                           Payment Non-Recurring Charge, an amount equal to
                           the after-tax sum of any Litigation Settlement
                           Payment Non-Recurring Charge taken by Borrower
                           during such fiscal quarter shall be ignored.
                           Finally, in calculating the consolidated net
                           income of Borrower and its Subsidiaries for any
                           quarter for the purposes of this subparagraph, an
                           amount equal to the after-tax sum of any
                           Acquisition In-Process R&D Charges taken by
                           Borrower during such fiscal quarter shall be
                           ignored.

                  (h) SCHEDULE I which sets forth the Proportionate Share of
         each Lender is hereby amended to read in its entirety as set forth
         on ATTACHMENT A hereto.

         4. REPRESENTATIONS AND WARRANTIES. Borrower hereby represents and
warrants to Agent, the Existing Lenders and the New Lender that the following
are true and correct on the date of this Amendment and that, after giving
effect to the amendments set forth in PARAGRAPH 3 above, the following will
be true and correct on the Second Amendment Effective Date:

                  (a) The representations and warranties of Borrower and its
         Subsidiaries set forth in PARAGRAPH 4.01 OF THE CREDIT AGREEMENT and
         in the other Credit Documents are true and correct in all material
         respects;

                  (b) No Default or Event of Default has occurred and is
         continuing; and

                  (c) Each of the Credit Documents is in full force and
         effect.

                                       5
<PAGE>

(Without limiting the scope of the term "Credit Documents," Borrower
expressly acknowledges in making the representations and warranties set forth
in this PARAGRAPH 4 that, on and after the date hereof, such term includes
this Amendment.)

         5. SECOND AMENDMENT EFFECTIVE DATE. The addition of the New Lender
as a party to the Credit Agreement effected by PARAGRAPH 2 above and the
amendments effected by PARAGRAPH 3 above shall become effective on January
28, 2000 (the "SECOND AMENDMENT EFFECTIVE DATE"), subject to receipt by the
Existing Lenders, the New Lender and Agent, as applicable, on or prior to the
Second Amendment Effective Date of the following, each in form and substance
satisfactory to the Existing Lenders, the New Lender and Agent and their
respective counsel, as applicable:

                  (a) This Amendment duly executed by Borrower, each Lender
         and Agent;

                  (b) An Amended and Restated Note, dated the Closing Date
         and otherwise appropriately completed, made payable to the New
         Lender, in the amount of the New Lender's Proportionate Share as of
         the Second Amendment Effective Date;

                  (c) A letter in the form of ATTACHMENT B hereto
         appropriately completed and duly executed by each Guarantor;

                  (d) A Certificate of the Secretary of Borrower, dated the
         Second Amendment Effective Date, certifying that (i) the Articles of
         Incorporation and Bylaws of Borrower, in the form delivered to Agent
         on the Closing Date, are in full force and effect and have not been
         amended, supplemented, revoked or repealed since such date and (ii)
         that attached thereto are true and correct copies of resolutions
         duly adopted by the Board of Directors of Borrower and continuing in
         effect, which authorize the execution, delivery and performance by
         Borrower of this Amendment and the consummation of the transactions
         contemplated hereby, including without limitation, the increase in
         the Total Commitment;

                  (e) A Certificate of the Secretary of each Domestic
         Subsidiary, dated the Second Amendment Effective Date, certifying
         that (i) the Articles of Incorporation and Bylaws of such Domestic
         Subsidiary, in the form delivered to Agent on the Closing Date or
         the First Amendment Effective Date (as applicable), are in full
         force and effect and have not been amended, supplemented, revoked or
         repealed since such date and (ii) that attached thereto are true and
         correct copies of resolutions duly adopted by the Board of Directors
         of such Domestic Subsidiary and continuing in effect, which
         authorize the execution, delivery and performance by such Domestic
         Subsidiary of the Credit Documents executed or to be executed by
         such Subsidiary in connection with this Amendment and the
         consummation of the transactions contemplated hereby and thereby;

                  (f) A favorable written opinion of legal counsel for
         Borrower and the Domestic Subsidiaries, dated the Second Amendment
         Effective Date, addressed to Agent for the benefit of Agent, the
         Existing Lenders and the New Lender, covering such legal

                                       6
<PAGE>

         matters as Agent may reasonably request and otherwise in form and
         substance satisfactory to Agent; and

                  (g) Such other evidence as Agent, any Existing Lender or
         the New Lender may reasonably request to establish the accuracy and
         completeness of the representations and warranties and the
         compliance with the terms and conditions contained in this Amendment
         and the other Credit Documents.

         6. EFFECT OF THIS AMENDMENT. On and after the Second Amendment
Effective Date, each reference in the Credit Agreement and the other Credit
Documents to the Credit Agreement shall mean the Credit Agreement as amended
hereby. Except as specifically amended above, (a) the Credit Agreement and
the other Credit Documents shall remain in full force and effect and are
hereby ratified and confirmed and (b) the execution, delivery and
effectiveness of this Amendment shall not, except as expressly provided
herein, operate as a waiver of any right, power, or remedy of the Lenders or
Agent, nor constitute a waiver of any provision of the Credit Agreement or
any other Credit Document.

         7.  MISCELLANEOUS.

                  (a) COUNTERPARTS. This Amendment may be executed in any
         number of identical counterparts, any set of which signed by all the
         parties hereto shall be deemed to constitute a complete, executed
         original for all purposes.

                  (b) HEADINGS. Headings in this Amendment are for
         convenience of reference only and are not part of the substance
         hereof.

                  (c) GOVERNING LAW. This Amendment shall be governed by and
         construed in accordance with the laws of the State of California
         without reference to conflicts of law rules.

                                       7
<PAGE>

         IN WITNESS WHEREOF, Borrower, Agent, the Existing Lenders and the
New Lender have caused this Amendment to be executed as of the day and year
first above written.

BORROWER:                              ADAC LABORATORIES

                                       By:
                                          ---------------------------------
                                          Name:
                                                ---------------------------
                                          Title:
                                                ---------------------------

AGENT:                                 ABN AMRO BANK N.V.

                                       By:
                                          ---------------------------------
                                          Name:
                                                ---------------------------
                                          Title:
                                                ---------------------------

                                       By:
                                          ---------------------------------
                                          Name:
                                                ---------------------------
                                          Title:
                                                ---------------------------

EXISTING LENDERS:                      ABN AMRO BANK N.V.

                                       By:
                                          ---------------------------------
                                          Name:
                                                ---------------------------
                                          Title:
                                                ---------------------------

                                       By:
                                          ---------------------------------
                                          Name:
                                                ---------------------------
                                          Title:
                                                ---------------------------

                                       SANWA BANK CALIFORNIA

                                       By:
                                          ---------------------------------
                                          Name:
                                                ---------------------------
                                          Title:
                                                ---------------------------

                                       8
<PAGE>

                                       BANQUE NATIONALE DE PARIS

                                       By:
                                          ---------------------------------
                                          Name:
                                                ---------------------------
                                          Title:
                                                ---------------------------

                                       By:
                                          ---------------------------------
                                          Name:
                                                ---------------------------
                                          Title:
                                                ---------------------------

                                       UNION BANK OF CALIFORNIA, N.A.

                                       By:
                                          ---------------------------------
                                          Name:
                                                ---------------------------
                                          Title:
                                                ---------------------------

                                       WELLS FARGO BANK, N.A.

                                       By:
                                          ---------------------------------
                                          Name:
                                                ---------------------------
                                          Title:
                                                ---------------------------

NEW LENDER:                            COMERICA BANK - CALIFORNIA

                                       By:
                                          ---------------------------------
                                          Name:
                                                ---------------------------
                                          Title:
                                                ---------------------------

                                       9
<PAGE>

                                  ATTACHMENT A

                                     LENDERS

LENDER                                                           PROPORTIONATE
                                                                     SHARE*

ABN AMRO BANK N.V.                                                29.41176471%

                  APPLICABLE LENDING OFFICE:

                  ABN AMRO Bank N.V.
                  San Francisco Representative Office
                  101 California Street, Suite 4550
                  San Francisco, CA  94111-5812

                  ADDRESS FOR NOTICES:

                  CREDIT ADMINISTRATION:

                  ABN AMRO Bank N.V.
                  208 S. LaSalle Street, Suite 1500
                  Chicago, IL  60604-1003
                  Attn:  Joseph Coriaci
                         Credit Administration
                  Telephone:  (312) 992-5118
                  Fax No.:  (312) 992-5111

                  With a copy to:

                  ABN AMRO Bank N.V.
                  101 California Street, Suite 4550
                  San Francisco, CA 94111-5812
                  Attn:  Dianne Barkley
                         Vice President
                  Telephone:  (415) 984-3706
                  Fax No:  (415) 362-3524

                                      A-1
<PAGE>

                  NOTICES OF BORROWING, ETC.:

                  ABN AMRO Bank N.V.
                  Capital Markets Syndication Group
                  1235 Avenue of the Americas, 9th Floor
                  New York, NY 10019
                  Attn:  Linda Boardman
                  Telephone:  (212) 314-1724
                  Fax No:  (212) 314-1709

                  WIRING INSTRUCTIONS:

                  ABN AMRO Bank N.V.
                  ABA #:  026009580
                  F/O ABN AMRO Bank N.V.
                  Chicago Branch CPU
                  Account #:  650-001-1789-41
                  Reference:  Adac Laboratories

         * To be expressed as a percentage rounded to the eighth digit to the
           right of the decimal point.

                                      A-2
<PAGE>

LENDER                                                             PROPORTIONATE
                                                                       SHARE*

SANWA BANK CALIFORNIA                                               21.17647059%

                  Applicable Lending Office:
                  San Jose CBC
                  220 Almaden Boulevard
                  San Jose, CA  95113-2003

                  Address for notices:

                  220 Almaden Boulevard
                  San Jose, CA  95113-2003
                  Attn:  James Rosewater
                  Telephone No:  (408) 297-6500
                  Telecopier No:  (408) 292-4092

                  Wiring Instructions:

                  Sanwa Bank California
                  220 Almaden Boulevard
                  San Jose, CA  95113
                  ABA No. 122003516
                  Account No:  1129-92463
                  Reference:  Commercial Loan No. 00-0491250-5
                  For Further Credit To: ADAC Laboratories

         * To be expressed as a percentage rounded to the eighth digit to the
           right of the decimal point.

                                      A-3
<PAGE>

LENDER                                                            PROPORTIONATE
                                                                      SHARE*

BANQUE NATIONALE DE PARIS                                          12.94117647%

                  Applicable Lending Office:

                  Banque National de Paris,
                  San Francisco Branch
                  180 Montgomery Street, 3rd Floor
                  San Francisco, CA  94104

                  Address for Notice:

                  180 Montgomery Street, 3rd Floor
                  San Francisco, CA  94104
                  Attention:  Debra Wright, Vice President
                  Telephone:  (415) 956-0707
                  Telecopier:  (415) 296-8954
                  Telex:  RCA 278900 (Answerback: BNPs UR)

                  Wiring Instructions

                  Federal Reserve Bank of San Francisco
                  San Francisco, California
                  ABA Number:  121027234
                  Account Name:  Banque Nationale de Paris, San Francisco Branch
                  Reference:  ADAC Laboratories

         * To be expressed as a percentage rounded to the eighth digit to the
           right of the decimal point.

                                      A-4
<PAGE>

LENDER                                                             PROPORTIONATE
                                                                       SHARE*

UNION BANK OF CALIFORNIA, N.A.                                      12.94117647%

                  Applicable Lending Office:

                  Union Bank of California, N.A.
                  350 California Street
                  San Francisco, CA  94104
                  Address for Notice:                        CC: NOTIFICATION

                  Union Bank of California, N.A.             Allan Miner
                  Northern California Commercial Banking     99 Almaden Blvd.
                    Division                                 Suite 200
                  350 California Street, 10th Floor          San Jose, CA 95113
                  San Francisco, CA  94104                   Tel.: 408/279-7742
                  Attention:  Jim Goudy                      Fax: 408/280-7163
                  Telephone:  (415) 705-7165
                  Telecopier:  (415) 705-7111

                  Wiring Instructions:

                  Union Bank of California, N.A.
                  1980 Saturn Street
                  Monterey Park, CA  91755

                  ABA Number:  122-000-496
                  Account Number:  070-196431
                  Account Name:  Wire Transfer Clearing
                  Attention:  Commercial Loan Operations
                  Reference:  ADAC Laboratories
                  (include any additional information needed to process
                  transaction)

         * To be expressed as a percentage rounded to the eighth digit to the
           right of the decimal point.

                                      A-5
<PAGE>

LENDER                                                            PROPORTIONATE
                                                                      SHARE*

WELLS FARGO BANK, N.A.                                             11.76470588%

                  Applicable Lending Office:

                  Wells Fargo Bank, N.A.
                  121 Park Center Plaza, Third Floor
                  San Jose, CA  95113

                  Address for Notice:

                  Wells Fargo Bank, N.A.
                  Commercial Banking Loan Center
                  201 Third Street, 8th Floor
                  San Francisco, CA  94103
                  Attention:  Carol Burke
                  Telephone:  (415) 477-5260
                  Telecopier:  (415) 979-0675

                  Wiring Instructions:

                  Wells Fargo Bank, N.A.
                  San Francisco, CA
                  ABA Number:  121-000-248
                  BNF:  Member SYN/AC-2712-507201
                  Reference:  ADAC LABORATORIES

         * To be expressed as a percentage rounded to the eighth digit to the
           right of the decimal point.

                                      A-6
<PAGE>

LENDER                                                             PROPORTIONATE
                                                                       SHARE*

COMERICA BANK-CALIFORNIA                                            11.76470588%

                  Applicable Lending Office:

                  Comerica Bank-California
                  155 Grand Avenue, Suite 402
                  Oakland, CA  94612

                  Address for Notice:

                  Comerica Bank-California
                  155 Grand Avenue, Suite 402
                  Oakland, CA  94612
                  Attention:  Scott Smith
                  Telephone:  (510) 645-2202
                  Telecopier:  (510) 645-2220

                  Wiring Instructions:

                  Comerica Bank-California
                  San Jose, California
                  ABA Number:  1211-37522
                  BNF:  For credit of CLS Wire Suspense A/C 21585-90010
                  Reference:  ADAC Laboratories
                  Attention:  Scott Smith (510) 645-2202

         * To be expressed as a percentage rounded to the eighth digit to the
           right of the decimal point.

                                      A-7
<PAGE>

                                  ATTACHMENT B

                            GUARANTOR CONSENT LETTER

                                January [A], 2000

TO:      ABN AMRO BANK, N.V.,
         As Agent for the Lenders under the Credit Agreement referred to below

         1.       Reference is made to the following:

                  (a) The Amended and Restated Credit Agreement dated as of
         March 29, 1999, as amended by that certain First Amendment to Credit
         Agreement dated as of August 17, 1999 (the "CREDIT AGREEMENT") among
         ADAC Laboratories ("BORROWER"), the financial institutions which are
         from time to time parties thereto (the "LENDERS"), and ABN AMRO
         Bank, as agent for the Lenders ("AGENT");

                  (b) The Amended and Restated Guaranty dated as of March 29,
         1999 (the "GUARANTY") executed by each of the undersigned (each a
         "GUARANTOR," and collectively, the "GUARANTORS") in favor of the
         Lenders and Agent; and

                  (c) The Second Amendment to Credit Agreement dated as of
         January 28, 2000 (the "SECOND AMENDMENT") among Borrower, the
         Lenders and Agent.

         2. Each Guarantor hereby consents to the Second Amendment including
without limitation the increase of the Total Commitment from $75,000,000 to
$85,000,000. Each Guarantor expressly agrees that such amendment shall in no
way affect or alter the rights, duties, or obligations of Guarantor, the
Lenders or Agent under the Guaranty.

         3. From and after the date hereof, the term "Credit Agreement" as
used in the Guaranty shall mean the Credit Agreement, as amended by the
Second Amendment.

         4. The Guarantors' consent to the Second Amendment shall not be
construed (i) to have been required by the terms of the Guaranty or any other
document, instrument or agreement relating thereto or (ii) to require the
consent of the Guarantors in connection with any future amendment of the
Credit Agreement or any other Credit Document.

         IN WITNESS WHEREOF, each Guarantor has executed this Guarantor
Consent Letter as of the day and year first written above.

                                       ADAC RESEARCH AND MFG., INC.

                                       By:
                                          ------------------------------------
                                          Name:
                                                ------------------------------
                                          Title:
                                                ------------------------------

                                      B-1
<PAGE>

                                       ADAC HEALTHCARE INFORMATION
                                       SYSTEMS, INC.

                                       By:
                                          ------------------------------------
                                          Name:
                                                ------------------------------
                                          Title:
                                                ------------------------------

                                       ADAC LABORATORIES PACIFIC, INC.

                                       By:
                                           ------------------------------------
                                           Name:
                                                 ------------------------------
                                           Title:
                                                 ------------------------------

                                       ADAC CAPITAL, LLC

                                       By:
                                           ------------------------------------
                                           Name:
                                                 ------------------------------
                                           Title:
                                                 ------------------------------

                                      B-2<PAGE>
                                                                    Exhibit 10.1

                             STOCK OPTION AGREEMENT

                  THIS STOCK OPTION AGREEMENT (this "Agreement") is entered into
as of February 11, 2000, by and among CORNERSTONE PROPERTIES INC., a Nevada
corporation ("Cornerstone"), EQUITY OFFICE PROPERTIES TRUST, a Maryland real
estate investment trust ("EOP"), DEUTSCHE BANK AG der Deutschen Bank, a stock
corporation organized under German law ("Deutsche Bank"), and DEUTSCHER HEROLD
LEBENSVERSICHERUNGS-AG, a stock corporation organized under German law and an
indirect subsidiary of Deutsche Bank ("Deutscher Herold").

                  In consideration of the mutual covenants and agreements
contained herein and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, and intending to be legally bound
hereby, the parties hereto hereby agree as follows:

                                    ARTICLE I
                                THE STOCK OPTION

                  1.1 GRANT OF STOCK OPTION. Each of Deutsche Bank and Deutscher
Herold hereby grant to each of Cornerstone and EOP (each, a "Purchaser") an
irrevocable option (the "Stock Option") to purchase, subject to the terms
hereof, the number of fully paid and non-assessable shares of 7.0% Cumulative
Convertible Preferred Stock, with no par value, of Cornerstone ("Cornerstone
Preferred Stock") set forth on SCHEDULE A attached hereto opposite its name,
subject to adjustment pursuant to Section 5 hereof (such shares of Cornerstone
Preferred Stock held by Deutsche Bank and Deutscher Herold are referred to
collectively as the "Option Shares"), at a purchase price of $18.00 in cash per
share of Cornerstone Preferred Stock or, if the Merger Agreement (as defined
herein) is amended to increase the price per share of a share of Cornerstone
common stock, no par value, in excess of $18.00 per share, then at a purchase
price in cash equal to such greater price per share of Cornerstone common stock,
no par value, as is so specified in the Merger Agreement, as so amended, in each
case together with the dividends accrued and unpaid to the date of the Option
Closing (the "Purchase Price"), and in the manner set forth in Sections 1.2, 1.3
and 1.4 hereof.

                  1.2  EXERCISE OF THE STOCK OPTION.

                           (a) The Stock Option may be exercised by Cornerstone
or EOP, in whole but not in part, at any time or from time to time prior to
termination of the Stock Option in accordance with this Section 1.2 and Section
9.8 hereof.

                           (b) If at any time Cornerstone desires to exercise
the Stock Option, Cornerstone shall (1) deliver to each of Deutsche Bank and
Deutscher Herold a written notice (a "Cornerstone Exercise Notice," with the
date of the

<PAGE>

Cornerstone Exercise Notice being hereinafter called the "Cornerstone Notice
Date") notifying each of Deutsche Bank and Deutscher Herold of its exercise of
the Stock Option and (2) on the Cornerstone Notice Date, deliver to EOP a copy
of the Cornerstone Exercise Notice. The closing of such exercise by Cornerstone
of the Stock Option (the "Cornerstone Option Closing") shall occur on the third
business day immediately following the Cornerstone Notice Date at a time and at
a place in New York, New York designated by Cornerstone in the Cornerstone
Exercise Notice. "Business Day" means a business day in Frankfurt, Bonn and New
York.

                           (c) Subject to Section 1.2(d) hereof, if at any time
EOP desires to exercise the Stock Option, EOP shall (1) deliver to each of
Deutsche Bank and Deutscher Herold a written notice (an "EOP Exercise Notice,"
with the date of the EOP Exercise Notice being hereinafter called the "EOP
Notice Date") notifying each of Deutsche Bank and Deutscher Herold of its
exercise of the Stock Option and (2) on the EOP Notice Date, deliver to
Cornerstone a copy of the EOP Exercise Notice; PROVIDED, HOWEVER, that EOP shall
not be entitled to exercise the Stock Option or to deliver an EOP Exercise
Notice if Cornerstone has delivered a Cornerstone Exercise Notice in accordance
with the terms of this Agreement and the date for the Cornerstone Option Closing
corresponding to such Cornerstone Option Closing, as set forth in Section 1.2(b)
hereof, has not passed. Subject to Section 1.2(d) hereof, the closing of such
exercise by EOP of the Stock Option (the "EOP Option Closing") shall occur on
the ninth business day immediately following the EOP Notice Date at a time and
at a place in New York, New York designated by EOP in the EOP Exercise Notice.

                           (d) Upon receipt of an EOP Exercise Notice,
Cornerstone shall have the right, exercisable at any time prior to 5:00 p.m.,
New York time, on the second business day after the EOP Notice Date, to (1)
deliver to each of Deutsche Bank and Deutscher Herold a Cornerstone Exercise
Notice notifying each of Deutsche Bank and Deutscher Herold of its exercise of
the Stock Option and (2) on the Cornerstone Notice Date, deliver to EOP a copy
of the Cornerstone Exercise Notice. If Cornerstone so exercises the Stock
Option, the Cornerstone Option Closing shall occur on the third business day
immediately following the Cornerstone Notice Date at a time and at a place in
New York, New York designated by Cornerstone in the Cornerstone Exercise Notice.
Upon Cornerstone's purchase of the Option Shares pursuant thereto, the EOP
Exercise Notice delivered pursuant to Section 1.2(d) shall be deemed of no force
or effect.

                           (e) Upon receipt of a Cornerstone Exercise Notice,
each of Deutsche Bank and Deutscher Herold shall be obligated, provided that the
conditions specified in Section 1.3 hereto shall be satisfied, to deliver to
Cornerstone a certificate or certificates evidencing the Option Shares held by
it, in accordance with the terms of this Agreement, on the third business day
immediately following the Cornerstone Notice Date.

                                      -2-
<PAGE>

                           (f) On the date set for closing of any purchase of
Option Shares hereunder, each of Deutsche Bank and Deutscher Herold shall,
subject to satisfaction of the conditions specified in Section 1.3 hereof and
receipt of the Purchase Price therefor, deliver to Purchaser (i) a certificate
or certificates representing the Option Shares held by it, properly endorsed or
otherwise in proper form for transfer, and (ii) an irrevocable proxy in form
reasonably acceptable to Purchaser authorizing Purchaser or its designee to vote
such Option Shares on all matters submitted to a vote of the holders of
Cornerstone Preferred Stock.

                  1.3 CONDITIONS TO DELIVERY OF THE OPTION SHARES. The right of
each of Cornerstone or EOP to exercise the Stock Option and the obligation of
each of Deutsche Bank and Deutscher Herold to deliver the Option Shares held by
it upon the exercise of the Stock Option are subject to the following
conditions:

                           (a) Such delivery would not violate in any material
respect, or otherwise cause a material violation of, any material Law (as
defined herein), including, without limitation, under the Hart-Scott-Rodino
Antitrust Improvements Act of 1976, as amended ("Hart-Scott-Rodino"), applicable
to such exercise of Stock Option and the delivery of the Option Shares; and

                           (b) There shall be no preliminary or permanent
injunction or other order by any court of competent jurisdiction preventing or
prohibiting such exercise of the Stock Option or the delivery of Option Shares
in respect of such exercise.

                  1.4 CLOSING. At the Option Closing, Cornerstone or EOP, as
applicable, shall pay to each of Deutsche Bank and Deutscher Herold, upon
receipt of the certificate or certificates and proxy pursuant to Section 1.2(f),
the aggregate Purchase Price for Option Shares to be purchased by Cornerstone or
EOP, as applicable (net of any taxes required to be held pursuant to Section
1445 of the Internal Revenue Code of 1986, as amended), by wire transfer of
immediately available funds to an account(s) designated by each of Deutsche Bank
and Deutscher Herold at least two business days prior to the Option Closing.

                  1.5 ADJUSTMENTS UPON SHARE ISSUANCES, CHANGES IN
CAPITALIZATION, ETC. In the event of any change in the Cornerstone Preferred
Stock or in the number of outstanding shares of Cornerstone Preferred Stock by
reason of a stock dividend, split-up, recapitalization, combination, exchange of
shares or similar transaction or any other change in the corporate or capital
structure of Cornerstone (including, without limitation, the declaration or
payment of an extraordinary dividend in the form of cash, securities or other
property), the type and number of shares or securities to be delivered by
Deutsche Bank and Deutscher Herold upon exercise of the Stock Option shall be
adjusted appropriately.

                                      -3-
<PAGE>

                                   ARTICLE II
               REPRESENTATIONS AND WARRANTIES OF DEUTSCHE BANK AND
                                DEUTSCHER HEROLD

                  Each of Deutsche Bank and Deutscher Herold hereby represents
and warrants to each of Cornerstone and EOP as follows:

                  2.1 AUTHORITY RELATIVE TO THIS AGREEMENT. It has all requisite
corporate power and authority to execute and deliver this Agreement, to perform
its obligations hereunder and to consummate the transactions contemplated hereby
to be consummated by it. The execution and delivery of this Agreement by it and
the consummation by it of the transactions contemplated hereby have been duly
authorized by all necessary corporate action, and no other corporate proceedings
on the part of it are necessary to authorize the execution and delivery of this
Agreement or to consummate the transactions contemplated hereby. This Agreement
has been duly executed and delivered by it and constitutes the legal, valid and
binding obligations of it, enforceable against it in accordance with its terms,
subject to applicable bankruptcy, insolvency, moratorium or other similar Laws
relating to creditors' rights and general principles of equity.

                  2.2 NO LIENS. The Option Shares shall be delivered free and
clear of all security interests, liens, claims, pledges, options, rights of
first refusal, agreements, limitations on voting rights, charges and other
encumbrances of any nature whatsoever (other than this Agreement).

                  2.3 NO VIOLATION. The execution and delivery of this Agreement
by it do not, the performance of its obligations hereunder by it will not, the
consummation by it of the transactions contemplated to be performed by it
hereunder will not and the exercise by Cornerstone or EOP of the Stock Option
hereunder will not, (i) violate or conflict with any provision of any judgment,
order, decree, statute, law, ordinance, rule or regulation (collectively,
"Laws") in effect on the date of this Agreement and applicable to it (it being
understood that neither Deutsche Bank nor Deutscher Herold makes any
representation or warranty with respect to Hart-Scott-Rodino); (ii) require it
to obtain any consent, waiver, approval, license or authorization or permit of,
or make any filing with, or notification to, any governmental entities, based on
laws, rules, regulations and other requirements of governmental entities in
effect as of the date of this Agreement (it being understood that neither
Deutsche Bank nor Deutscher Herold makes any representation or warranty with
respect to Hart-Scott-Rodino); (iii) require the consent, waiver, approval,
license or authorization of any person (other than a governmental entity and
other than the property trustee (Deckungsstocktreuhander) of Deutscher Herold);
(iv) violate, conflict with or result in a breach of any obligation under, or
constitute a default (or an event which with notice or the lapse of time or both
would become a default) under, or give to others any rights of, or result in
any, termination, amendment, acceleration or cancellation of, or loss of any
benefit or

                                      -4-
<PAGE>

creation of a right of first refusal, or require any payment under, any
provision of any indenture, mortgage, note, bond, lien, lease, license,
agreement, contract, order, judgment, ordinance, permit or other instrument or
obligation to which it is a party or by which it is bound or subject to; or (v)
conflict with or violate the articles or certificate of incorporation or bylaws,
or the equivalent organizational documents, in each case as amended or restated,
of it.

                                   ARTICLE III
                  REPRESENTATIONS AND WARRANTIES OF CORNERSTONE

                  Cornerstone hereby represents and warrants to each of Deutsche
Bank and Deutscher Herold that it has all requisite corporate power and
authority to execute and deliver this Agreement, to perform its obligations
hereunder and to consummate the transactions contemplated hereby to be
consummated by Cornerstone. The execution and delivery of this Agreement by
Cornerstone have been duly authorized by the Board of Directors of Cornerstone.
This Agreement has been duly executed and delivered by Cornerstone and
constitutes the legal, valid and binding obligations of it, enforceable against
it in accordance with its terms, subject to applicable bankruptcy, insolvency,
moratorium or other similar laws relating to creditors' rights and general
principles of equity.

                                   ARTICLE IV
                            COVENANTS OF CORNERSTONE

                  Cornerstone hereby covenants and agrees that it shall acquire
Option Shares and/or other securities acquired upon its exercise of the Stock
Option for investment purposes only and not with a view to any distribution
thereof in violation of the Securities Act of 1933, as amended (the "Securities
Act"), and immediately shall cancel the Option Shares upon their purchase by
Cornerstone hereunder.

                                    ARTICLE V
                      REPRESENTATIONS AND WARRANTIES OF EOP

                  EOP hereby represents and warrants to each of Deutsche Bank
and Deutscher Herold that it has all requisite trust power and authority to
execute and deliver this Agreement, to perform its obligations hereunder and to
consummate the transactions contemplated hereby to be consummated by EOP. The
execution and delivery of this Agreement by EOP have been duly authorized by the
Board of Trustees of EOP. This Agreement has been duly executed and delivered by
EOP and constitutes the legal, valid and binding obligations of it, enforceable
against it in accordance with its terms, subject to applicable bankruptcy,
insolvency,

                                      -5-
<PAGE>

moratorium or other similar laws relating to creditors' rights and general
principles of equity.

                                   ARTICLE VI
                                COVENANTS OF EOP

                  EOP hereby covenants and agrees that it shall acquire Option
Shares and/or other securities acquired upon its exercise of the Stock Option
for investment purposes only and not with a view to any distribution thereof in
violation of the Securities Act, and shall not sell any such securities
purchased pursuant to this Agreement except in compliance with the Securities
Act.

                                   ARTICLE VII
                 COVENANTS OF DEUTSCHE BANK AND DEUTSCHER HEROLD

                  Each of Deutsche Bank and Deutscher Herold shall not, directly
or indirectly, and shall cause each of its affiliates not to, directly or
indirectly, (a) sell, transfer, pledge, encumber, assign or otherwise dispose
of, or enter into any contract, option or other agreement or understanding with
respect to the sale, transfer, pledge, encumbrance, assignment or other
disposition of, Option Shares, (b) grant any proxies for any Option Shares, (c)
deposit any Option Shares into a voting trust or enter into a voting agreement
with respect to any Option Shares, or tender any Option Shares in a transaction,
or (d) take any action which is intended to have the effect of preventing or
disabling Deutsche Bank or Deutscher Herold from performing its obligations
under this Agreement; PROVIDED, HOWEVER, that nothing herein shall prevent the
sale, transfer, pledge or assignment of any of such Option Shares, provided that
the purchaser, transferee, pledgee or assignee thereof agrees in writing to be
bound by the terms of this Agreement. To enable either of the Purchasers to
enforce the transfer restrictions contained in this Article VII, each of
Deutsche Bank and Deutscher Herold hereby consents to the placing of
stop-transfer orders with the transfer agent of the Cornerstone Preferred Stock.

                                      -6-
<PAGE>

                                  ARTICLE VIII
                          WAIVER OF DISSENTERS' RIGHTS

                  Each of Deutsche Bank and Deutscher Herold hereby irrevocably
and forever waives any and all rights it may have under Chapter 92A of the
General Corporation Law of Nevada with respect to any of the transactions
contemplated by that certain Merger Agreement, dated as of February 11, 2000, by
and among EOP, EOP Partnership, Cornerstone and Cornerstone Partnership (the
"Merger Agreement"). Notwithstanding the foregoing, the foregoing waiver shall
be of no force or effect after December 31, 2000.

                                   ARTICLE IX
                                  MISCELLANEOUS

                  9.1 EXPENSES. Except as expressly provided herein to the
contrary, each party hereto shall pay all of its expenses in connection with the
transactions contemplated by this Agreement, including, without limitation, the
fees and expenses of its counsel and other advisors.

                  9.2 NOTICES. All notices and other communications given or
made pursuant hereto shall be in writing and shall be given (and shall be deemed
to have been duly given upon receipt) by delivery in person, by telecopy or
facsimile, by registered or certified mail (postage prepaid, return receipt
requested), or by a nationally recognized courier service to the parties at the
following addresses (or at such other address for a party as shall be specified
by like changes of address) or, if sent by telecopy or facsimile, to the parties
at the telecopier numbers specified below:

<TABLE>
<S>                                          <C>
                  If to Cornerstone:         Cornerstone Properties Inc.
                                             126 East 56th Street
                                             New York, NY  10022
                                             Attention: Lee Van Boven, Esq.
                                             Telecopier: 650-345-8264

                  With a copy                King & Spalding
                  (which shall not           191 Peachtree Street
                  constitute notice) to:     Atlanta, GA 30303-1763
                                             Attention: William B. Fryer, Esq.
                                             Telecopier: 404-572-5100
</TABLE>

                                      -7-
<PAGE>

<TABLE>
<S>                                          <C>
                  If to EOP:                 Equity Office Properties Trust
                                             Two North Riverside Plaza
                                             Chicago, IL 60606
                                             Attention: Stanley M. Stevens, Esq.
                                             Telecopier: 312-559-5021

                  With copies                Hogan & Hartson L.L.P.
                  (which shall not           555 13th Street, N.W.
                  constitute notice) to:     Washington, D.C. 20004
                                             Attention: J. Warren Gorrell, Jr., Esq.
                                                        George P. Barsness, Esq.
                                             Telecopier: 202-637-5910

                  If to Deutsche Bank:       Deutsche Bank AG
                                             Group Investments
                                             Taunusanlage 12
                                             60325 Frankfurt am Main
                                             GERMANY
                                             Attention: Lutz Robra
                                             Telecopier: 49 69 910-43583

                  With a copy                White & Case LLP
                  (which shall not           1155 Avenue of the Americas
                  constitute notice) to:     New York, NY 10036
                                             Attention: Duane D. Wall, Esq.
                                             Telecopier: (212) 819-8200

                  If to Deutscher Herold:    Deutscher Herold Lebensversicherungs-AG
                                                 der Deutschen Bank
                                             Poppelsdorfer Allee 25-33
                                             53115 Bonn
                                             GERMANY
                                             Attention: Mr. J. Klahn
                                             Telecopier: 49 228 268 3838

                  With copies                 White & Case LLP
                  (which shall not            1155 Avenue of the Americas
                  constitute notice) to:      New York, NY 10036
                                              Attention: Duane D. Wall, Esq.
                                              Telecopier: (212) 819-8200
</TABLE>

                                      -8-
<PAGE>

                  9.3 ENTIRE AGREEMENT. This Agreement constitutes the entire
agreement between the parties and supersedes all prior agreements and
understandings, both written and oral, between the parties, or any of them, with
respect to the subject matter hereof.

                  9.4 ASSIGNMENT. Neither this Agreement nor any rights or
obligations hereunder shall be assigned by operation of law or otherwise,
without the prior written consent of the other party hereto; PROVIDED, HOWEVER,
that EOP may assign this Agreement or any of its rights or obligations hereunder
to EOP Operating Limited Partnership, a Delaware limited partnership ("EOP
Partnership"), without the consent of any other party hereto; PROVIDED, FURTHER,
HOWEVER, that Cornerstone may assign this Agreement or any of its rights or
obligations hereunder to Cornerstone Properties Limited Partnership, a Delaware
limited partnership ("Cornerstone Partnership"), without the consent of any
other party hereto (PROVIDED, HOWEVER, that Cornerstone Partnership agrees to
cause Cornerstone to cancel the Option Shares immediately upon any purchase by
Cornerstone Partnership hereunder).

                  9.5 GOVERNING LAW. This Agreement, and all matters relating
hereto, shall be governed by, and construed in accordance with the laws of the
State of Maryland, regardless of the laws that might govern under applicable
principles of conflict of law theory.

                  9.6 CONSENT TO JURISDICTION; WAIVER OF JURY TRIAL. Each of
Deutsche Bank and Deutscher Herold hereby submits and consents to non-exclusive
personal jurisdiction in any action, suit or proceeding arising out of this
Agreement or the transactions contemplated hereby (and for no other purposes) in
a federal court located in the State of Maryland or in a Maryland state court.
Any process, summons, notice or document delivered by mail to the address set
forth in Section 9.2 shall be effective service of process for any action, suit
or proceeding in any Maryland state court or any federal court located in the
State of Maryland with respect to any matters to which Deutsche Bank or
Deutscher Herold has submitted to jurisdiction in this Section 9.6. Each of
Deutsche Bank and Deutscher Herold irrevocably and unconditionally waives any
objection to the laying of venue of any action, suit or proceeding arising out
of this Agreement or the transactions contemplated hereby in any Maryland state
court or any federal court located in the State of Maryland, and hereby
irrevocably and unconditionally waives and agrees not to plead or claim in any
such court that any such action, suit or proceeding brought in any such court
has been brought in an inconvenient forum. EACH OF DEUTSCHE BANK AND DEUTSCHER
HEROLD IRREVOCABLY WAIVES TRIAL BY JURY IN ANY ACTION, SUIT OR PROCEEDING WITH
RESPECT TO THIS AGREEMENT.

                  9.7 INJUNCTIVE RELIEF. The parties agree that in the event of
a breach of any provision of this Agreement irreparable damage would occur, the
aggrieved

                                      -9-
<PAGE>

party would be without an adequate remedy at law and damages would be difficult
to determine. The parties therefore agree that in the event of a breach of any
provision of this Agreement, the aggrieved party may elect to institute and
prosecute proceedings in any court of competent jurisdiction to enforce specific
performance or to enjoin the continuing breach of such provision. By seeking or
obtaining such relief, the aggrieved party shall not be precluded from seeking
or obtaining any other relief to which it may be entitled at law or in equity.

                  9.8 TERMINATION. The Stock Option shall terminate upon the
earlier of: (i) the consummation of the Cornerstone Option Closing or the EOP
Option Closing hereunder; (ii) the date which is the tenth day after the
termination of the Merger Agreement; or (iii) December 31, 2000.

                  9.9 COUNTERPARTS. This Agreement may be executed in any number
of counterparts, each of which shall be deemed to be an original and all of
which together shall constitute one and the same document.

                  9.10 SEVERABILITY. Any term or provision of this Agreement
which is invalid or unenforceable in any jurisdiction shall, as to such
jurisdiction, be ineffective to the extent of such invalidity or
unenforceability without rendering invalid or unenforceable the remaining terms
and provisions of this Agreement or affecting the validity or enforceability of
any of the terms or provisions of this Agreement in any other jurisdiction. If
any provision of this Agreement is so broad as to be unenforceable, such
provision shall be interpreted to be only so broad as to make it enforceable.

                  9.11 FURTHER ASSURANCES. Each party hereto shall execute and
deliver all such further documents and take all such further action as may be
necessary in order to consummate the transactions contemplated by this
Agreement.

                  9.12 THIRD PARTY BENEFICIARIES. Nothing in this Agreement,
expressed or implied, shall be construed to give any person other than the
parties hereto and their successors and permitted assigns any legal or equitable
right, remedy or claim under or by reason of this Agreement or any provision
contained herein.

                  9.13 AMENDMENT AND MODIFICATION. This Agreement may be
amended, modified and supplemented only by a written document executed by
Cornerstone, EOP, Deutsche Bank and Deutscher Herold.

                  9.14 TREATMENT OF CORNERSTONE PREFERRED STOCK IN THE MERGER.
Each share of Cornerstone Preferred Stock shall be converted in the Merger into
the right to receive $18.00, together with accrued and unpaid dividends to the
Effective Time of the Merger, in cash, as described in Section 1.10(b)(iii) of
the Merger Agreement.

                  9.15 PUT RIGHT. In the event that the Stock Option is not
exercised within two business days after the Effective Time of the Merger, each
of Deutsche

                                      -10-
<PAGE>

Bank and Deutscher Herold shall have the right to require EOP to purchase the
Option Shares in the same manner and with the same effect as if EOP shall have
given an EOP Exercise Notice, whereupon EOP shall be required to purchase such
Option Shares in accordance with this Agreement.

                                      -11-

<PAGE>

                  IN WITNESS WHEREOF, the parties have caused this Agreement to
be executed as of the date first written above by their respective officers
thereunto duly authorized.

                         CORNERSTONE PROPERTIES INC.

                         By:   /s/ John S. Moody
                         ---------------------------
                         Name:  John S. Moody
                         Title: President and Chief
                                Executive Officer

                         EQUITY OFFICE PROPERTIES TRUST

                         By:   /s/ Stanley M. Stevens
                         ----------------------------
                         Name:  Stanley M. Stevens
                         Title: Executive Vice President
                                and Chief Legal Counsel

                         DEUTSCHE BANK AG

                         By:   /s/ Lutz Robra             /s/ Gerald F. Bender
                         ---------------------------      ----------------------
                         Name:  Lutz Robra                Gerald F. Bender
                         Title: Director                  Senior Associate
                                                            Director

                         DEUTSCHER HEROLD
                         LEBENSVERSICHERUNGS-AG

                         By:   /s/ K.R. Vias              /s/ J. Klahn
                         ---------------------------      ---------------------
                         Name:  K.R. Vias                 J. Klahn
                         Title: Director                  Director

                                      -12-
<PAGE>

                                   SCHEDULE A

                           Cornerstone Properties Inc.
                    7% Cumulative Convertible Preferred Stock

Deutsche Bank AG                                         2,249,053 shares

Deutscher Herold Lebensversicherungs-AG                    781,250 shares

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