<PAGE>

                                                                   Exhibit 10.14



                                EXECUTION VERSION

           This FIRST AMENDMENT (this "AMENDMENT"), dated as of May 10, 1999, to
the SECOND AMENDED AND RESTATED REVOLVING CREDIT AND GUARANTY AGREEMENT, dated
as of November 3, 1998 (as the same has been supplemented and is now in effect,
the "Loan Agreement"), is by and among: (i) CORNERSTONE PROPERTIES INC., a
corporation duly organized and validly existing under the laws of Nevada
("Cornerstone"); (ii) CORNERSTONE PROPERTIES LIMITED PARTNERSHIP, a Delaware
limited partnership ("Cornerstone LP"; together with Cornerstone, the
"Borrowers," and each a "Borrower"); (iii) each of the direct and indirect
Subsidiaries of the Borrowers that is a signatory hereto identified under the
caption "GUARANTORS" on the signature pages thereto; (iv) each of the financial
institutions that is a signatory hereto identified under the caption "LENDERS"
on the signature pages thereto (individually, a "LENDER" and, collectively, the
"LENDERS"); (v) BANKERS TRUST COMPANY, as Administrative Agent for the Lenders
thereunder (in such capacity, the "ADMINISTRATIVE AGENT"); (vi) THE CHASE
MANHATTAN BANK, as Syndication Agent for the Lenders thereunder (in such
capacity, the "SYNDICATION AGENT"); and (vii) NATIONSBANK, N.A., as
Documentation Agent for the Lenders thereunder (the "DOCUMENTATION AGENT," and
together with the Administrative Agent and the Syndication Agent, the "AGENTS").

                                R E C I T A L S:
                                - - - - - - - -

           WHEREAS, capitalized terms used herein and not otherwise defined
herein shall have the meanings assigned to such terms in the Loan Agreement; and

           WHEREAS, pursuant to the Loan Agreement, the Lenders have agreed to
make revolving loans to Cornerstone and Cornerstone LP in an aggregate principal
amount not to exceed $550,000,000; and

           WHEREAS, the Borrowers, the Guarantors, the Agents, and the Lenders
are willing, on the terms and subject to the conditions set forth below, to
amend the Loan Agreement (the Loan Agreement, as amended pursuant to the terms
of this Amendment, being referred to as the "AMENDED LOAN AGREEMENT");

      NOW, THEREFORE, the undersigned agree as follows:

      SECTION 1. AMENDMENTS TO LOAN AGREEMENT. Effective on (and subject to the
occurrence of) the First Amendment Effective Date (as such term is defined in
Section 4), the Loan Agreement is hereby amended in accordance with this Section
1; except as expressly amended by this Amendment, the Loan Agreement shall
continue in full force and effect in accordance with its terms:

      SECTION 1.1. AMENDMENTS TO SECTION 1.1. (i) Section 1.1 of the Loan
Agreement is amended by deleting clause (i) of the definition of the term
"Applicable Margin" in its entirety and inserting in lieu thereof the following:


<PAGE>

      "(i) for any date of calculation during any period during which neither
      Borrower has received a Minimum Long Term Debt Rating or during which all
      such ratings have been withdrawn by the applicable rating agency, the
      number of basis points ("bps") per annum opposite the Leverage Ratio
      (calculated as of the end of the immediately preceding fiscal quarter) set
      forth in the grid below under the caption "Applicable Eurodollar Margin"
      or "Applicable Unused Line Fee Margin," as the case may be:

<TABLE>
<CAPTION>
                                                     Applicable            Applicable
               Leverage Ratio                    Eurodollar Margin  Unused Line Fee Margin
----------------------------------------------   -----------------  ----------------------
<S>                                                    <C>                  <C>
          LESS THAN OR EQUAL TO .3                     110 bps              15 bps

GREATER THAN .3 but LESS THAN OR EQUAL TO .45          125 bps              15 bps

GREATER THAN .45 but LESS THAN OR EQUAL TO .55         140 bps              20 bps

              GREATER THAN .55                         180 bps              25 bps;
</TABLE>

      and".

      (ii) Section 1.1 of the Loan Agreement is further amended by adding
thereto the following definition in its appropriate alphabetical order:

      'LEVERAGE RATIO ADJUSTMENT DATE' shall mean the earliest to occur of

      (i) November 3, 2000, or

      (ii) the date on which the cash proceeds received by the Loan Parties
      since November 3, 1998 (net of reasonable and customary taxes and
      transaction costs actually paid) from all sales, transfers, or other
      dispositions of Properties and from all sales or other offerings of equity
      securities by the Loan Parties, exceeds $200,000,000 in the aggregate."

      SECTION 1.2. AMENDMENTS TO SECTION 8.6. Section 8.6 of the Loan Agreement
is amended by deleting Section 8.6 in its entirety and by inserting in lieu
thereof the following:

      "SECTION 8.6.  LEVERAGE RATIO.  (i) Permit the Leverage Ratio as
at the end of any fiscal quarter to exceed,

      (x) from and after the Execution Date until the Business Day immediately
      prior to the Leverage Ratio Adjustment Date, sixty per cent (60%), and

      (y) from and after the Leverage Ratio Adjustment Date, fifty-five per cent
      (55%).



                                       2
<PAGE>

      (ii) At any time the Leverage Ratio equals or exceeds fifty-five per cent
(55%), acquire or develop any real properties (other than those properties
listed on Schedule 8.6 hereto) not in the portfolio of the Loan Parties at such
time, if the effect of such acquisition or development would be to increase the
Leverage Ratio."

      SECTION 1.3. AMENDMENTS TO SECTION 8.10(I). Section 8.10(i) of the Loan
Agreement is amended by deleting the words "to be less than 2.00 to 1.00"
therefrom and by inserting in lieu thereof the words "to be less than (x) from
and after the Execution Date until the day immediately preceding the first
anniversary of the First Amendment Effective Date, 2.00 to 1.00, and (y) from
and after the first anniversary of the First Amendment Effective Date, 2.22 to
1.00".

      SECTION 1.4. AMENDMENTS TO SECTION 8.10(II). Section 8.10(ii) of the Loan
Agreement is amended by deleting the words "to be less than 2.50 to 1.00"
therefrom and by inserting in lieu thereof the words "to be less than (x) from
and after the Execution Date until November 2, 2000, 2.22 to 1.00, and (y) from
and after November 3, 2000, 2.50 to 1.00".

      SECTION  1.5.  NEW  SCHEDULES.   The  Loan  Agreement  is  hereby
amended  by adding  thereto a new  SCHEDULE  8.6,  in the form  annexed
hereto as Exhibit A.

            SECTION 2. REPRESENTATIONS, WARRANTIES AND COVENANTS.

           (a) CORPORATE POWER AND AUTHORITY. Each party hereto represents that
it has all requisite organizational power and authority to enter into and
perform its obligations under this Agreement. The execution, delivery and
performance of this Agreement have been duly authorized by all necessary
organizational action on the part of each such party.

           (b) COMPLIANCE WITH OTHER INSTRUMENTS, ETC. The Loan Parties hereby
jointly and severally represent that the consummation of the transactions
contemplated by this Amendment will not result in any breach of, or constitute a
default under, or result in the creation of any mortgage, lien, pledge, charge,
security interest or other encumbrance in respect of any property of either of
the Borrowers, any of the Guarantors or any of their Subsidiaries under, any
indenture, mortgage, deed of trust, bank loan or credit agreement, corporate
charter, by-law, or other agreement or instrument to which either of the
Borrowers, any of the Guarantors or any of their Subsidiaries is a party or by
which either of the Borrowers, any of the Guarantors, any of their Subsidiaries
or any of their properties may be bound or affected, or violate any existing
law, governmental rule or regulations, or any order of any court, arbitrator or
governmental body, applicable to either of the Borrowers, any of the Guarantors,
any of their Subsidiaries or any of their properties.

           (c) GOVERNMENTAL CONSENT. The Loan Parties hereby jointly and
severally represent that no consent, approval or authorization of, or
registration, filing or declaration with, any governmental



                                       3
<PAGE>

authority is required for the validity of the execution and delivery by the
Borrowers and the Guarantors of this Amendment or the consummation of the
transactions contemplated hereby, except for such consents, approvals or
authorizations which have been obtained or waived.

           SECTION 3. EXPENSES. Without limiting the generality of any provision
of the Loan Agreement, the Loan Parties hereby jointly and severally agree to
pay any invoices or statements submitted for the reasonable fees, expenses and
client charges of Willkie Farr & Gallagher, counsel for the Agents, for any
services rendered in connection with the transactions contemplated hereby and
with respect to this Amendment and any other document delivered pursuant to this
Amendment.

           SECTION 4. EFFECTIVENESS. This Amendment shall become effective on
the date (the "First Amendment Effective Date") of the delivery to the
Administrative Agent of a copy of this Amendment executed by the Lenders, the
Agents, the Borrowers, and the Guarantors.

           SECTION 5. COUNTERPARTS; SEPARATE AGREEMENTS. This Amendment may be
executed simultaneously in one or more counterparts, each of which shall be
deemed an original, but all of which together shall constitute one and the same
instrument.

           SECTION 6. FURTHER ASSURANCES. Each of the Borrowers and the
Guarantors hereby jointly and severally agrees that it will, and will cause each
of the other Loan Parties to, take any action that from time to time may be
reasonably necessary to effectuate the amendments contemplated herein.

           SECTION 7.  HEADINGS.  The headings of the several sections
of this Amendment are inserted for convenience only and shall not in
any way affect the meaning or construction of this Amendment.

           SECTION 8.  NO OTHER CHANGES.  (a)  Except as expressly
stated herein, the Loan Agreement is unaffected hereby and shall
remain in full force and effect in accordance with the terms thereof.

           (b) The Guarantors jointly and severally expressly agree that the
Loan Agreement and their obligations as Guarantors thereunder are unaffected
hereby and shall remain in full force and effect in accordance with the terms
thereof.

           (c) Except as expressly set forth herein, the Lenders do not waive
(i) any breaches or defaults under the Loan Agreement or any other agreements
executed concurrently therewith or pursuant thereto, whether known or unknown,
previously or hereafter arising, or of any nature or character whatsoever, or
(ii) any of their respective rights or remedies thereunder or under applicable
law.

           SECTION 9. REAFFIRMATION. The Borrowers and the Guarantors hereby
jointly and severally represent and warrant to the Lenders that



                                       4
<PAGE>

each of the representations and warranties contained in the Loan Agreement were
true and correct in all material respects when made and, except to the extent
(i) that a particular representation or warranty by its terms expressly applies
only to an earlier date, or (ii) the Borrowers have previously advised the
Lenders in writing as contemplated under the Loan Agreement, are true and
correct in all material respects as of the date of this Amendment.

           SECTION 10. FACILITY DOCUMENT PURSUANT TO LOAN AGREEMENT. This
Amendment is executed pursuant to the Loan Agreement, shall be a Facility
Document, and shall be construed, administered and applied in accordance with
all of the terms and provisions of the Loan Agreement (and, following the First
Amendment Effective Date, the Amended Loan Agreement). Any breach of any
representation or warranty or covenant or agreement contained in this Amendment
shall be deemed to be an Event of Default for all purposes of the Loan
Agreement.

           SECTION 11.  CROSS-REFERENCES.  References in this Amendment
to  any  Article  or  Section  are,  unless   otherwise   specified  or
otherwise  required by the context,  to such Article or Section of this
Amendment.

           SECTION 12.  SUCCESSORS AND ASSIGNS.  This  Amendment  shall
be  binding  upon and inure to the  benefit of the  parties  hereto and
their respective successors and assigns.

           SECTION 13.  GOVERNING LAW. THIS  AMENDMENT  SHALL BE DEEMED
TO BE A CONTRACT  MADE UNDER AND  GOVERNED  BY THE LAWS OF THE STATE OF
NEW YORK.






                                       5
<PAGE>






           IN WITNESS WHEREOF, the parties hereto have signed, or caused their
duly elected officer to sign on the date first written above.

                                 BORROWERS:

                                 CORNERSTONE PROPERTIES INC.


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


                                 CORNERSTONE PROPERTIES LIMITED
                                    PARTNERSHIP

                                 By:  CORNERSTONE PROPERTIES INC.,
                                      Its General Partner


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


<PAGE>



                                 GUARANTORS:

                                 CORNERSTONE DENVER LLC
                                 CORNERSTONE PEACHTREE LLC
                                 500 BOYLSTON CORNERSTONE LLC
                                 222 BERKELEY CORNERSTONE LLC
                                 125 SUMMER STREET CORNERSTONE LLC
                                 CORNERSTONE MINNEAPOLIS LLC
                                 CORNERSTONE NEW YORK LLC
                                 CORNERSTONE 11 CANAL CENTER LLC
                                 CORNERSTONE 99 CANAL LLC
                                 CORNERSTONE SEATTLE LLC

                                 By:  CORNERSTONE PROPERTIES LIMITED
                                      PARTNERSHIP, the sole member of
                                      each

                                      By:  CORNERSTONE PROPERTIES
                                           INC., its general partner


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


                                 CORPRO REAL ESTATE MANAGEMENT, INC.


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


                                 AGOURA HILLS BUSINESS PARK ASSOCIATES, LLC
                                 TEN ALMADEN ASSOCIATES, LLC
                                 18301 ASSOCIATES, LLC
                                 110 ATRIUM PLACE ASSOCIATES, LLC
                                 BIXBY OFFICE PARK ASSOCIATES, LLC
                                 66 BOVET ASSOCIATES, LLC
                                 490 CALIFORNIA ASSOCIATES, LLC
                                 2300 CR ASSOCIATES, LLC
                                 EMBARCADERO PLACE ASSOCIATES, LLC
                                 HACIENDA PLAZA ASSOCIATES, LLC
                                 ISLAND CORPORATE CENTER ASSOCIATES, LLC
                                 2677 MAIN STREET ASSOCIATES, LLC
                                 4550 NCR ASSOCIATES, LLC
                                 4600 NCR ASSOCIATES, LLC
                                 OFFICE OPPORTUNITY ASSOCIATES, LLC
                                 PARK PLAZA ASSOCIATES, LLC
                                 PRUNEYARD ASSOCIATES, LLC


<PAGE>



                                 429 SANTA MONICA ASSOCIATES, LLC
                                 SEAPORT PLAZA ASSOCIATES, LLC
                                 SEARISE ASSOCIATES, LLC
                                 5300 SOUTH ASSOCIATES, LLC
                                 WARNER PARK ASSOCIATES, LLC
                                 WEST WILSHIRE ASSOCIATES, LLC
                                 WESTLAKE SPECTRUM ASSOCIATES, LLC
                                 WESTLAKE SPECTRUM TWO ASSOCIATES, LLC
                                 2700 YGNACIO ASSOCIATES, LLC

                                 By:  CORNERSTONE HOLDINGS, LLC, the
                                      managing member of each

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

                                 BAY PARK PLAZA ASSOCIATES, L.P.
                                 BILTMORE LAKES ASSOCIATES, L.P.
                                 CENTERSIDE ASSOCIATES, L.P.
                                 2000 CROW CANYON ASSOCIATES, L.P.
                                 2010 CROW CANYON ASSOCIATES, L.P.
                                 1300 EL CAMINO ASSOCIATES, L.P.
                                 188 EMBARCADERO ASSOCIATES, L.P.
                                 GATEWAY PHOENIX ASSOCIATES, L.P.
                                 GBC UNIVERSITY ASSOCIATES, L.P.
                                 700 NORTH BRAND ASSOCIATES, L.P.
                                 PENINSULA OFFICE PARK ASSOCIATES, L.P.
                                 1737 NORTH FIRST STREET ASSOCIATES, L.P.
                                 ONE BAY PLAZA ASSOCIATES, L.P.
                                 7373 SCOTTSDALE ASSOCIATES, L.P.
                                 5990 SEPULVEDA ASSOCIATES, L.P.
                                 1301 SHOREWAY ASSOCIATES, L.P.
                                 1600 SOUTH MAIN ASSOCIATES, L.P.
                                 5820 STONERIDGE ASSOCIATES, L.P.
                                 1320 WILLOW PASS ASSOCIATES, L.P.
                                 1390 WILLOW PASS ASSOCIATES, L.P.
                                 SECOND AND MAIN ASSOCIATES
                                 BAYHILL ASSOCIATES
                                 CAMPUS DRIVE INVESTMENT COMPANY
                                 CROSSROADS LIMITED
                                 EXPOSITION CENTRE ASSOCIATES, L.P.

                                 By:  CORNERSTONE HOLDINGS, LLC, the
                                      general partner of each


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


<PAGE>



                                 CORNERSTONE COMMERCE PARK HOLDINGS, LLC
                                 CORNERSTONE BAYHILL HOLDINGS, LLC
                                 CORNERSTONE HOLDINGS, LLC
                                 CORNERSTONE DEERFIELD LLC
                                 ONE MEMORIAL CORNERSTONE LLC
                                 60 STATE STREET CORNERSTONE LLC
                                 CORNERSTONE WILSHIRE-CAL LLC

                                 By:  CORNERSTONE PROPERTIES LIMITED
                                      PARTNERSHIP, the sole member of
                                      each

                                      By:  CORNERSTONE PROPERTIES
                                           INC., its general partner


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



                                 201 CALIFORNIA LLC
                                 1299 OCEAN LLC

                                 By:  CORNERSTONE WILSHIRE-CAL LLC,
                                      the sole member of each

                                      By:  CORNERSTONE PROPERTIES
                                           LIMITED PARTNERSHIP, its
                                           sole member

                                         By:  CORNERSTONE PROPERTIES
                                               INC., its general
                                               partner


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



<PAGE>








                                 AGENTS AND LENDERS:

                                 BANKERS TRUST COMPANY
                                      as Administrative Agent and
                                      Lender


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




                                 THE CHASE MANHATTAN BANK
                                      as Syndication Agent and Lender


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




                                 NATIONSBANK, N.A.
                                      as Documentation Agent and
                                      Lender


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




                                 THE BANK OF NOVA SCOTIA
                                    as Lender


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




                                 COMMERZBANK AKTIENGESELLSCHAFT,
                                 NEW YORK BRANCH
                                      as Lender


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





<PAGE>




                                 KEYBANK NATIONAL ASSOCIATION
                                      as Lender


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




                                 PNC BANK, NATIONAL ASSOCIATION
                                      as Lender


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




                                 SUMMIT BANK
                                      as Lender


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




                                 CITIZENS BANK OF RHODE ISLAND
                                      as Lender


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




                                 MELLON BANK, N.A.
                                      as Lender


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




<PAGE>





                                 MICHIGAN NATIONAL BANK
                                      as Lender


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




                                 FIRST AMERICAN BANK TEXAS, SSB
                                      as Lender


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




                                 CREDIT LYONNAIS, NEW YORK BRANCH
                                      as Lender


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




                                 AMSOUTH BANK
                                      as Lender


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




                                 U.S. BANK NATIONAL ASSOCIATION
                                      as Lender


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




<PAGE>




                                 THE BANK OF NEW YORK
                                      as Lender


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




                                 UNION BANK OF CALIFORNIA
                                      as Lender


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


<PAGE>



                                 EXHIBIT A

                                 SCHEDULE 8.6


Piper Jaffray Center, Minneapolis, Minnesota

Concar, San Mateo, California

One Powell, San Fransisco, California

1st and Howard, San Fransisco, California

Seaport Plaza, Redwood City, California

The Ferry Building, San Fransisco, California

Larkspur Landing, Larkspur, California

Pruneyard Inn, Campbell, California