Document:

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                                                                   EXHIBIT 10.4

                              EMPLOYMENT AGREEMENT

     THIS AGREEMENT, is made and entered into as of June 27, 2000, by and
between Mack-Cali Realty Corporation, a Maryland corporation (the "Company"),
and Michael V. Prentiss (the "Executive"), and the effective date of which shall
be the date of the closing (the "Closing") of the merger (the "Merger") of
Prentiss Properties Trust, a Maryland real estate investment trust (the "Trust")
with the Company:

                              W I T N E S S E T H:

     WHEREAS, Executive currently serves as the Chairman of the Board of
Trustees of the Trust;

     WHEREAS, in connection with the merger of the Trust into the Company (the
"Merger") the Company and Executive desire to enter into this Agreement to
provide for Executive's employment with the Company and to provide for Executive
serving as Co-Chairman of the Board of Directors of the Company;

     WHEREAS, the parties acknowledge and agree that following the Closing the
terms of this Agreement shall supersede all prior agreements between Executive
and the Trust except with respect to any payments and benefits due Executive
pursuant to Section B, Paragraph 9 of the Amended and Restated Employment
Agreement, dated as of May 10, 2000, between Executive and the Trust (the "Old
Agreement").

     NOW, THEREFORE, IN CONSIDERATION of the mutual covenants, promises and
obligations of the parties provided for in this Agreement and the benefits to be
received by Executive, and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree as follows:

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     A.   DEFINITIONS.

     For purposes of this Agreement, the following terms shall have the
following meanings (applicable to both the singular and plural forms of the
terms defined):

     1. "Acquisition of Office or Industrial Property" means engaging in the
activity of soliciting, seeking to acquire, obtaining an option or first right
of refusal to acquire, or acquiring, any interest in an Office or Industrial
Property or in real property planned for development as an Office or Industrial
Property.

     2. "Affiliate" means (i) any person directly or indirectly controlling,
controlled by, or under common control with such other person, (ii) any
executive officer, director, trustee or general partner of such other person,
and (iii) any legal entity for which such person acts as an executive officer,
director, trustee or general partner. The term "person" means and includes any
natural person, corporation, partnership, association, limited liability company
or any other legal entity.

     3. "Board" means the Board of Directors of the Company.

     4. "Change in Control" shall mean that (a) the Company has consummated the
proposed transaction(s) set forth in any agreement the Company enters into with
a person or entity that involves the transfer of ownership of the Company or of
more than fifty (50%) percent of the Company's total assets or earnings power on
a consolidated basis, as reported in the Company's consolidated financial
statements filed with the Securities and Exchange Commission (including an
agreement for the acquisition of the Company by merger, consolidation, or
statutory share exchange regardless of whether the Company is intended to be the
surviving or resulting entity after the merger, consolidation, or statutory
share exchange or for the sale of substantially all of the Company's assets to
the person or

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entity), (b) as the direct or indirect result of, or in connection with, a cash
tender or exchange offer, a merger or other business combination or combinations
of these transactions, the persons who were directors of the Company before such
transactions cease to constitute a majority of the Board, or any successor's
board, within two years of the last such transaction, or (c) during any period
of two consecutive calendar years, the Continuing Directors cease for any reason
to constitute a majority of the Board. For purposes of the preceding sentence,
"Continuing Director" means any member of the Board, while a member of the Board
and (I) who was a member of the Board prior to the Effective Date or (2) whose
subsequent nomination or election to the Board was recommended or approved by a
majority of the Continuing Directors.

     5. "Competitive Activity" means engaging in directly, through an Affiliate,
or being employed by any entity undertaking, or otherwise undertaking to do any
of the following: (i) Acquisition of Office or Industrial Property, (ii) Office
or Industrial Property Ownership or Leasing, (iii) Office or Industrial Property
Construction, (iv) Office or Industrial Property Entitlements, (v) Speculation,
or (vi) Office or Industrial Property Management and Operation.

     6. "Effective Date" means the date on which the Closing occurs.

     7. "Employment Term " means a period commencing on the Effective Date and
continuing until the fifth anniversary of the Effective Date, unless terminated
earlier as provided herein.

     8. "Good Reason" means

             (a) a reduction by the Company of Executive's annual base salary;
             (b) an assignment of duties to Executive that are materially

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inconsistent with his duties hereunder;
             (c) relocation of Executive's office in contravention of
subparagraph 4(f) of Section B; or
             (d) the intentional breach by the Company of any material provision
of this Agreement that continues for a period of 14 days after the Board
receives written notice of such breach.

     9. "Office or Industrial Property" means any Property that is used in whole
or in part for office or industrial space or office or industrial related
purposes, whether in fee or leasehold, together with all improvements and
fixtures now or hereafter located thereon, all rights, privileges and easements
appurtenant thereto, and all tangible and intangible personal property used in
connection therewith.

     10. "Office or Industrial Property Construction" means the construction,
renovation or repair of improvements on an Office or Industrial Property by
Executive or an Affiliate of Executive.

     11. "Office or Industrial Property Entitlements" means engaging in the
process by which a person with an interest in an Office or Industrial Property
obtains necessary or desirable governmental approvals, licenses, permits,
entitlements or agreements for the commencement of Office or Industrial Property
Construction.

     12. "Office or Industrial Property Management and Operation" means engaging
in directly or through an Affiliate, or being employed by any entity
undertaking, or otherwise undertaking the day-to-day management and operation of
an Office or Industrial Property, whether pursuant to a master lease, management
agreement or any other arrangement.

     13. "Property" means any real property or any interest therein.

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     14. "Speculation" means engaging in the activity of soliciting, seeking to
acquire, obtaining an option or a first right of refusal to acquire, or
acquiring, any interest in an Office or Industrial Property with the intention
at any time of acquiring (or obtaining an option or a first right of refusal to
acquire) or holding an Office or Industrial Property for subsequent sale or
other transfer to any person for purposes of Competitive Activity.

     15. "Termination Without Cause" means the termination of Executive's
employment by the Company for any reason other than Voluntary Termination or
Termination With Cause.

     16. "Termination With Cause" means the termination of Executive's
employment by act of the Board of Directors of the Company due to (a) willful
failure of Executive to perform his duties hereunder that continues for a period
of fourteen (14) days after Executive receives written notice thereof from the
Company, (b) Executive either directly or indirectly entering into a Competitive
Activity in violation of this Agreement that continues for a period of fourteen
(14) days after Executive receives written notice thereof from the Company, (c)
Executive's misappropriation of funds or property of the Company or any of its
Affiliates or (d) Executive's admission or conviction of fraud against the
Company or any of its Affiliates.

     17. "Termination for Lack of Economic Interest" means the termination of
Executive's employment by the Company in the event that he does not continue to
hold at least sixty-five (65%) percent of the shares of the Company held by
Executive immediately after the Effective Date.

     18. "Voluntary Termination" means Executive's voluntary termination of his
employment hereunder for any reason other than Good Reason.

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     B.   POSITION ON THE BOARD OF DIRECTORS; THE EMPLOYMENT RELATIONSHIP.

     1. EMPLOYMENT/BOARD OF DIRECTORS. Executive shall serve in the capacity of
Co-Chairman of the Board for the length of the Employment Term, subject to
earlier termination as herein provided (I.E., Executive shall tender his
resignation from the Board effective at the end of the Employment Term and shall
further execute any documents confirming such resignation as required by the
Company).

     2. DUTIES. Executive shall have oversight responsibility with respect to
the integration of the business and the senior managers of the Trust with that
of the Company. Executive shall also advise the Chief Executive Officer and
regional directors of the Company with respect to real estate development and
acquisitions and will assist the Company in securing new investment and
development opportunities. Executive shall coordinate the performance of his
duties with the Chief Executive Officer of the Company, shall use his name to be
helpful to the Company, and shall analyze potential deals sourced by the
Company. The Company acknowledges that Executive will not be working in a
full-time capacity but will only devote such time and effort as he deems
appropriate with respect to the foregoing.

     3. COMPENSATION.

     (a) The Company initially shall pay Executive an annual base salary of
$350,000, to be paid in semi-monthly payments. Beginning on January 1, 2002, and
at the beginning of each calendar year thereafter in the Employment Term,
Executive's annual base salary shall be increased by ten (10%) percent.

     (b) In addition, on the Effective Date, the Company shall grant Executive a
warrant (the "Warrant") to purchase 500,000 shares of Company common stock. The

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Warrant shall vest in its entirety and become exercisable on the earlier of: (i)
the third anniversary of the Effective Date (the "Vesting Date") or (ii) a
Change in Control; shall have a per share exercise price of $29.15, shall have a
term of not less than ten (10) years and shall have such other terms and
conditions as shall be set forth in the agreement evidencing the Option.

     4. BENEFITS. The Company agrees to provide Executive with the following
benefits during the Employment Term:

        (a) EMPLOYEE BENEFITS. Executive shall be entitled to all rights,
benefits and privileges to which management level employees of the Company are
entitled, including, but not limited to, any retirement, pension,
profit-sharing, insurance, hospital or other plans which may now be in effect or
which may hereafter be adopted by the Company.

        (c) TAX AND ESTATE PLANNING. The Company shall provide Executive with
comprehensive annual personal tax and estate planning services including tax
planning for Executive's gross income. In addition, the Company shall provide
the services of an accountant to keep Executive's financial records and to
assist in tax reporting. Tax planning and accounting services shall be provided
in-house by the Company, or at Executive's option, by the firm of Arthur
Andersen or such other accounting firm as Executive may select, in his sole
discretion. Further, the estate planning services shall be provided by Sandy
Bisingano or such other professional as Executive shall select, in his sole
discretion. The Company shall pay for the full cost of such services at the
customary commercial rates charged by such service providers.

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        (c) COUNTRY CLUB FEES. The Company shall reimburse Executive for his
membership dues at the following country clubs: Brookhollow Golf Club in Dallas,
Texas; Robert Trent Jones Golf Club in Northern Virginia; Preston Trails Club in
Dallas, Texas; and Oyster Harbors Club in Cape Cod, Massachusetts.

        (d) FLIGHT TIME. Executive shall be provided with 100 hours per year of
flight time on a Challenger (the " Aircraft") through Flex Jets. At Executive's
discretion, such hours may be used in the performance of his duties hereunder or
for personal use. If the Company or an Affiliate owns the interest in the
Aircraft, then the Company shall pay all costs associated with the Aircraft;
provided however, that during the last two years of the Employment Term, the
cost that the Company shall pay shall not exceed $500,000 per year; and further
provided, that if any of such hours are used for Executive's personal use,
Executive shall reimburse the Company at the variable hourly rate for such
usage. If Executive owns the interest in the Aircraft, then the Company or an
Affiliate shall reimburse Executive for (i) the interest costs on the loan for
the acquisition of the interest in the Aircraft, (ii) the monthly management fee
associated with the interest in the Aircraft and (iii) the variable hourly rate
for usage of the Aircraft for business purposes. The Company and Executive agree
that the method and structure of providing the benefit to Executive under this
subparagraph 4(d) of Section B may be revised, provided, however, that no
reduction in benefits occurs.

        (e) REGISTRATION RIGHTS. Any shares of common stock of the Company owned
by Executive shall be covered by the registration rights agreement between
Executive and the Company attached hereto as Exhibit A.

        (f) OFFICE; SECRETARIAL ASSISTANCE. The Company shall maintain an office

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for Executive and provide Executive with secretarial assistance during the
Employment Term in the Dallas, Texas area comparable to the office and
secretarial assistance provided to Executive by the Trust. Executive's office
shall not be relocated more than five (5) miles from the Dallas area without
Executive's consent.

        5. EXPENSES. The Company recognizes that Executive will have to incur
certain out-of-pocket expenses, including, but not limited to, travel expenses,
related to his employment and the Company's business, and the Company agrees to
reimburse Executive for all reasonable expenses necessarily incurred by him in
the performance of his duties upon presentation of a voucher or documentation
indicating the amount and business purposes of any such expenses.

        6. TERMINATION IN CASE OF DEATH OR DISABILITY. In case of Executive's
death or permanent disability (defined as complete physical or mental inability,
confirmed by a licensed physician, to perform substantially all of the duties
described herein that continues for a period of 180 consecutive days), the
Company may elect to terminate Executive's employment pursuant to the terms of
Section B, Paragraph 8 hereof.

        7. TERMINATION WITH CAUSE; TERMINATION FOR LACK OF ECONOMIC INTEREST;
VOLUNTARY TERMINATION. The Company may terminate this Agreement upon a
determination that an event has occurred within the definition of Termination
With Cause or that Executive's reduced holding of Company stock falls within the
definition of a Termination for Lack of Economic Interest. If Executive shall
suffer Termination With Cause, Termination for Lack of Economic Interest, or
shall cease being employed by the Company on account of a Voluntary Termination,
then Executive shall receive accrued annual base salary and expense
reimbursement until the effective date of the Termination With Cause,

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Termination for Lack of Economic Interest or Voluntary Termination and shall not
be entitled to any annual base salary or expense reimbursement applicable to any
time after the effective date of the Termination With Cause, Termination for
Lack of Economic Interest or Voluntary Termination (except salary accrued but
unpaid on the date of such event). If any such termination takes place within 3
years of the Effective Date, then Executive shall receive the benefits listed in
clause (ii) of the first sentence of Paragraph 8 of Section B of the Old
Agreement on the same terms and conditions listed in such Paragraph until the
third anniversary of the Effective Date. Any period during which benefits are
continued pursuant to this Paragraph 7 of Section B shall be considered to be in
satisfaction of the Company's obligation to provide "continuation coverage"
pursuant to Section 4980B of the Internal Revenue Code of 1986, as amended (the
"Code"), and the period of coverage under Section 4980B shall be reduced by the
period during which benefits are provided pursuant to this Paragraph 7 of
Section B.

        8. DEATH OR DISABILITY; TERMINATION WITHOUT CAUSE; TERMINATION OF
EMPLOYMENT BY EXECUTIVE FOR GOOD REASON; OR RESIGNATION FOLLOWING A CHANGE IN
CONTROL. If the Company terminates Executive's employment due to his death or
disability or Company terminates Executive's employment in a Termination Without
Cause, or if Executive shall terminate his employment hereunder for Good Reason,
or shall resign for any reason or no reason within one year after a Change in
Control, then the Company: (i) shall pay Executive, or his estate, as the case
may be, within 30 days of such death, disability, termination or resignation, as
the case may be, (a) in the case of a termination of Executive's employment due
to death or disability, cash compensation in a lump sum equal to one year's
annual base salary, based on Executive's annual base salary at the

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time of such death or termination due to disability; or (b) in the case of a
Termination Without Cause or a termination of employment by Executive for Good
Reason or a resignation after a Change in Control, cash compensation in a lump
sum equal to $5,000,000; and (ii) continue to provide for a period of three
years after such death, disability or termination, at its expense, on behalf of
Executive and his dependents (a) annual physicals, medical, health, dental and
prescription drug benefits, (b) long-term disability coverage, (c) life
insurance and other death benefits coverage, and (d) all the benefits and
privileges set forth in subparagraphs (b), (c), (d), and (e) of Paragraph 4 of
Section B. For the same three-year period (except in the case of death),
Executive shall be entitled to retain, at the Company's expense, his current
office or a similar office and a secretary. The coverage and benefits (including
deductibles, costs and contributions by Executive, if any) provided under this
Paragraph 8 of Section B shall be no less favorable to Executive and his
dependents than the most favorable of such coverage and benefits provided
Executive and his dependents during the 90-day period immediately prior to such
death, disability or termination. The obligation under this Paragraph 8 of
Section B with respect to the foregoing benefits shall be limited if Executive
obtains any such benefits pursuant to a subsequent employer's benefit plans, in
which case the Company may reduce or eliminate the coverage and benefits it is
required to provide Executive hereunder as long as the aggregate coverage and
benefits of the combined benefit plans is no less favorable to Executive than
the coverage and benefits required to be provided hereunder. Any continued
rights and benefits that Executive, or Executive's estate or other legal
representatives, may have under employee benefit plans and programs of the
Company upon such death, disability or termination shall be determined in
accordance with the terms

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and provisions of such plans and programs. The foregoing notwithstanding, if
Executive has received, or is entitled to receive, the payments under Paragraph
9 of Section B, no payments or benefits shall be payable under this Paragraph 8.
Any period during which benefits are continued pursuant to this Paragraph 8 of
Section B shall be considered to be in satisfaction of the Company's obligation
to provide "continuation coverage" pursuant to Section 4980B of the Code, and
the period of coverage under Section 4980B shall be reduced by the period during
which benefits are provided pursuant to this Paragraph 8 of Section B.

     9. MEMBER OF BOARD AND INVESTMENT AND EXECUTIVE COMMITTEES. During the
Employment Term, Executive shall be nominated to serve as a member of the Board
and shall be appointed to the Investment Committee and the Executive Committee
of the Board. If during the Employment Term, Executive is (i) not elected to the
Board, (ii) is removed from the Board, (iii) is not appointed to either the
Investment Committee or the Executive Committee, (iv) is removed as a member of
the Investment Committee or the Executive Committee, (v) is not appointed as
Co-Chairman of the Board, or (vi) is removed as Co-Chairman of the Board, the
Company shall immediately pay Executive the sum of $5,000,000. In the event such
payment is made under this Paragraph 9 of Section B, and Executive's employment
is then terminated due to death, disability or any of the other conditions
covered by Paragraph 8 of Section B hereof during the Employment Term, Executive
shall not be entitled to any payment under clause (i) of the first sentence of
Paragraph 8 of Section B; provided, however, that in the event of any such
termination, Executive will be entitled to all the other benefits listed in such
Paragraph on the terms and conditions set forth therein.

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     10.  GROSS-UP PAYMENT.

     (a) In the event it shall be determined that any payment or distribution of
any type to or for the benefit of Executive, by the Company, any Affiliate, any
person who acquires ownership or effective control of the Company or ownership
of a substantial portion of the Company's assets (within the meaning of Section
280G of the Code and the regulations thereunder) or any Affiliate of such
person, whether paid or payable or distributed or distributable pursuant to any
of the terms of this Agreement or otherwise (the "Total Payments"), is or will
be subject to the excise tax imposed by Section 4999 of the Code or any interest
or penalties with respect to such excise tax (such excise tax, together with any
such interest and penalties, are collectively referred to as the "Excise Tax"),
then Executive shall be entitled to receive an additional payment (a "Gross-Up
Payment") in an amount such that after payment by Executive of all taxes
(including any interest or penalties imposed with respect to such taxes),
including any income tax, employment tax or Excise Tax, imposed upon the Gross
Up Payment, Executive retains an amount of the Gross-Up Payment equal to the
Excise Tax imposed upon the Total Payments.

     (b) All mathematical determinations, and all determinations as to whether
any of the Total Payments are "parachute payments" (within the meaning of
Section 280G of the Code), that are required to be made under this Subparagraph
(b), including determinations as to whether a Gross-Up Payment is required, the
amount of such Gross-Up Payment and amounts relevant to the last sentence of
this Subparagraph (b), shall be made by an independent accounting firm selected
by Executive from among the five (5) largest accounting firms in the United
States (the "Accounting Firm"), which shall provide its determination (the
"Determination"), together with detailed supporting calculations

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regarding the amount of any Gross-Up Payment and any other relevant matter, both
to the Company and Executive by no later than ten (10) days following the Change
in Control, or such earlier time as is requested by the Company or Executive (if
Executive reasonably believes that any of the Total Payments may be subject to
the Excise Tax). If the Accounting Firm determines that no Excise Tax is payable
by Executive, it shall furnish Executive and the Company with a written
statement that such Accounting Firm has concluded that no Excise Tax is payable
(including the reasons therefor) and that Executive has substantial authority
not to report any Excise Tax on his federal income tax return. If a Gross-Up
Payment is determined to be payable, it shall be paid to Executive within twenty
(20) days after the Determination (and all accompanying calculations and other
material supporting the Determination) is delivered to the Company by the
Accounting Firm. Any determination by the Accounting Firm shall be binding upon
the Company and Executive, absent manifest error. As a result of uncertainty in
the application of Section 4999 of the Code at the time of the initial
determination by the Accounting Firm hereunder, it is possible that Gross-Up
Payments not made by the Company should have been made ("Underpayment"), or that
Gross-Up Payments will have been made by the Company which should not have been
made ("Overpayments"). In either such event, the Accounting Firm shall determine
the amount of the Underpayment or Overpayment that has occurred. In the case of
an Underpayment, the amount of such Underpayment shall be promptly paid by the
Company to or for the benefit of Executive. In the case of an Overpayment,
Executive shall, at the direction and expense of the Company, take such steps as
are reasonably necessary (including the filing of returns and claims for
refund), follow reasonable instructions from, and procedures established by, the

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Company, and otherwise reasonably cooperate with the Company to correct such
Overpayment, provided, however, that (i) Executive shall not in any event be
obligated to return to the Company an amount greater than the net after-tax
portion of the Overpayment that he has retained or has recovered as a refund
from the applicable taxing authorities and (ii) this provision shall be
interpreted in a manner consistent with the intent of this Paragraph 10 of
Section B, which is to make Executive whole, on an after-tax basis, from the
application of the Excise Tax, it being understood that the correction of an
Overpayment may result in Executive repaying to the Company an amount which is
less than the Overpayment.

     C.   AGREEMENT NOT TO COMPETE.

     Except as explicitly provided herein, Executive agrees, for the entire
Employment Term, to the following covenants, effective within the United States:

     1. COMPETITIVE ACTIVITY RESTRICTION. Executive, personally or through any
Affiliate of Executive, shall not conduct any Competitive Activity unless
permitted pursuant to the terms of this Paragraph. A majority of the Board
members may determine that a Competitive Activity will not have a material
adverse effect on the operations of any Office or Industrial Property that the
Company either owns or has a right to acquire and permit Executive to enter into
a Competitive Activity. Notwithstanding any other provision of this Agreement,
Executive agrees that, during the time he is employed by the Company, Executive
shall first present to the Company all opportunities that arise to engage in
Competitive Activities. In the event the Company declines an opportunity that is
not in any sub-market in which the Company conducts its business, Executive
shall have the right to engage in that Competitive Activity. In the event that
the Competitive Activity is in any sub-

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market in which the Company conducts its business, Executive shall be prohibited
from engaging in such Competitive Activity.

     2. NO BENEFICIAL OWNERSHIP. Executive shall not beneficially own directly
or indirectly any beneficial interest in any entity engaged in any Competitive
Activity other than the Company, except for any interest in a company traded on
a nationally recognized public securities exchange (including The NASDAQ
National Market), provided such interest does not exceed five (5%) percent of
the outstanding capital stock of such company.

     3. LOANS. Executive shall not directly or indirectly make any loan to,
or hold any note evidencing a loan from, any entity engaged in any Competitive
Activity.

     4. COMPETITIVE ENTITY. Executive shall not be a director
or trustee, officer, or employee of, or consultant to (whether for compensation
or not) any entity engaged in any Competitive Activity.

     5. NOTIFICATION TO BOARD. If Executive or any Affiliate of Executive
desires to engage in any Competitive Activity, Executive shall describe fully
the proposed activity in a written notice (the "Disclosure Notice") to the
Board. A Disclosure Notice shall only pertain to a specific proposed project and
the referenced proposed project shall be described therein with specificity as
to timing, location, scope and the extent of Executive's involvement,
financially and in terms of his time commitment. A Disclosure Notice may not
request approval for any conceptual or non-project specific activity or for any
activity that is prohibited by this Agreement.

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     D.   MISCELLANEOUS PROVISIONS.

     1. NOTICES. All notices or deliveries authorized or required pursuant to
this Agreement shall be deemed to have been given when in writing and when (i)
deposited in the U.S. mail, certified, return receipt requested, postage
prepaid, or (ii) otherwise delivered by hand or by overnight delivery, against
written receipt, by a common carrier or commercial courier or delivery service
addressed to the parties at the following addresses or to such other addresses
as either may designate in writing to the other party:

         To the Company:   Mitchell E. Hersh
                           Chief Executive Officer
                           Mack-Cali Realty Corporation
                           11 Commerce Drive
                           Cranford, New Jersey  07016
                           (908) 272-8000

         With a Copy to:   Blake Hornick, Esq.
                           Pryor Cashman Sherman & Flynn LLP
                           410 Park Avenue
                           New York, New York  10022
                           (212) 326-0133

         To Executive:     Michael V. Prentiss
                           5006 Seneca Drive
                           Dallas, Texas  75209
                           (214) 350-3011

     2. ENTIRE AGREEMENT. This Agreement contains the entire understanding
between the parties hereto with respect to the subject matter hereof; provided,
however, that the payment and any benefits due Executive under Paragraph 9 of
Section B of the Old Agreement shall be paid or provided by the Company if such
amount has not been paid or such benefits have not been provided by the Trust
prior to the Merger, and further provided, that if any tax gross-up payment is
due Executive under Paragraph 10 of the Old Agreement, such amount shall be paid
by the Company if not paid by the Trust. This

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Agreement shall not be modified in any manner except by instrument in writing
signed, by or on behalf of, the parties hereto. This Agreement shall be binding
upon and inure to the benefit of the heirs, successors and assigns of the
parties hereto.

     3. EFFECTIVE DATE. Notwithstanding the date of this Agreement, the terms
and provisions of and rights and obligations under this Agreement shall become
effective on the Effective Date. In the event the Merger is not consummated,
this Agreement shall become null and void and have no further force or effect.

     4. APPLICABLE LAW. This Agreement shall be governed and construed in
accordance with the laws of the State of Maryland.

     5. ASSIGNMENT. Executive acknowledges that his services are unique and
personal. Executive may not assign his rights or delegate his duties or
obligations under this Agreement except (a) his rights to compensation and
benefits hereunder may be transferred by will or operation of law and (b) his
rights under employee benefit plans or programs described in Section B,
Paragraph 4(a) may be assigned or transferred in accordance with the terms of
such plans or programs, or regular practices thereunder. Executive's rights and
obligations under this Agreement shall inure to the benefit of and shall be
binding upon Executive's heirs and personal representatives.

     6. TITLES AND HEADINGS. Titles and headings to sections and paragraphs in
this Agreement are inserted for the convenience of reference only and are not
intended to be a part of or to affect the meaning or interpretation of this
Agreement.

     7. COUNTERPARTS. This Agreement may be executed in one or more
counterparts, each of which shall be deemed to be an original, but all of which
together shall constitute one and the same instrument.

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     8. AMENDMENTS. No amendment, modification or supplement to this Agreement
shall be binding on any of the parties hereto unless it is in writing and signed
by the parties in interest at the time of the modification, and further provided
any such modification is approved by a majority of the Board.

     9. NO THIRD-PARTY BENEFICIARIES. This Agreement is solely for the benefit
of the parties to this Agreement and should not be deemed to confer upon third
parties any remedy, claim, liability, reimbursement, claims or action or other
right in excess of those existing without reference to this Agreement.

     10. MAXIMUM LEGAL ENFORCEABILITY; TIME OF ESSENCE. Any provision of this
Agreement which is prohibited or unenforceable in any jurisdiction shall, as to
such jurisdiction, be ineffective to the extent of such prohibition or
unenforceability without invalidating the remaining provisions hereof. Any such
prohibition or unenforceability in any jurisdiction shall not invalidate or
render unenforceable such provision in any other jurisdiction. Without prejudice
to any rights or remedies otherwise available to any party to this Agreement,
each party hereto acknowledges that damages would not be an adequate remedy for
any breach of the provisions of this Agreement and agrees that the obligations
of the parties hereunder shall be specifically enforceable. Time shall be of the
essence as to each and every provision of this Agreement.

     11. SPECIFIC PERFORMANCE. Executive acknowledges that the obligations
undertaken by him pursuant to this Agreement are unique and that the Company
will not have an adequate remedy at law if he shall fail to perform any of his
obligations hereunder, and Executive therefore confirms that the Company's right
to specific performance of the terms of this Agreement is essential to protect
the rights, interest and goodwill of the

                                      19

<PAGE>

Company. Accordingly, in addition to any other remedies that the Company may
have at law or in equity, the Company shall have the right to have all
obligations, covenants, agreements and other provisions of this Agreement
specifically performed by Executive, and the Company shall have the right to
obtain preliminary and permanent injunctive relief to secure specific
performance and to prevent a breach or contemplated breach of this Agreement by
Executive. Executive acknowledges that the Company will have the right to have
the provisions of this Agreement enforced in any court of competent
jurisdiction, it being agreed that any breach or threatened breach of this
Agreement would cause irreparable injury to the Company and its business and
that money damages would not provide an adequate remedy to the Company.

     12. OPERATIONS OF AFFILIATED PARTIES. Executive agrees that he will refrain
from authorizing any Affiliate to perform any activities that would be
prohibited by the terms of this Agreement if they were performed by him.
Notwithstanding anything to the contrary contained in this Agreement, Executive
shall not be required by the terms of this Agreement to violate any fiduciary
duty existing on the date hereof that he owes to a third party.

     13 FURTHER ASSURANCES. The parties to this Agreement will execute and
deliver or cause the execution and delivery of such further instruments and
documents and will take such other actions as any other party to the Agreement
may reasonably request in order to effectuate the purpose of this Agreement and
to carry out the terms hereof.

                                      20

<PAGE>

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed as of the day and year first written above.

                                  EXECUTIVE

                                  /s/ Michael V. Prentiss
                                  ----------------------------
                                  Michael V. Prentiss

                                  MACK-CALI REALTY CORPORATION

                                  /s/ Mitchell E. Hersh
                                  ----------------------------
                                  Mitchell E. Hersh
                                  Chief Executive Officer

                                      21

<PAGE>

                                    EXHIBIT A
                                    ---------

                          REGISTRATION RIGHTS AGREEMENT

     This REGISTRATION RIGHTS AGREEMENT (this "AGREEMENT"), dated as of ______
____, 2000 is by and among Mack-Cali Realty Corporation, a Maryland corporation
(the "COMPANY"), and Michael V. Prentiss ("PRENTISS").

                                    RECITALS

     WHEREAS, Prentiss currently serves as the Chairman of the Board of Trustees
of Texas, a Maryland real estate investment trust (the "TRUST");

     WHEREAS, Prentiss has entered into an Employment Agreement, dated as of
June 27, 2000 by and between the Company and the Prentiss (the "EMPLOYMENT
AGREEMENT") the effective date of which will be the date of the closing of the
merger (the "MERGER") of the Trust with the Company; and

     WHEREAS, the Company and Prentiss desire to enter into this Agreement in
connection with Prentiss' employment by the Company after the Merger pursuant to
the Employment Agreement.

                                    AGREEMENT

     NOW, THEREFORE, in consideration of these premises and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged by Prentiss and the Company, the parties hereto agree as follows:

                                    SECTION 1
                                   DEFINITIONS

     1.1 SPECIFIC DEFINITIONS. The following terms are defined as follows:

     "AFFILIATE" is defined in Rule 12b-2 under the Exchange Act.

     "BOARD" means the Company's board of directors.

     "COMMON STOCK" means common stock, par value $0.01 per share, of the
      Company.

     "EXCHANGE ACT" means the Securities Exchange Act of 1934, as amended.

     "INDEMNIFIED PARTY" is defined in SECTION 6.3.

     "INDEMNIFYING PARTY" is defined in SECTION 6.3.

     "INSPECTORS" is defined in SECTION 3.1(j).

<PAGE>

     "LOSS" or "LOSSES" is defined in SECTION 6.1.

     "PERSON" means any business entity (including a corporation, partnership
(limited or general), limited liability company or business trust) or a natural
person.

     "REGISTER," "REGISTERED" and "REGISTRATION" and words of similar import
mean a registration effected by preparing and filing with the SEC a registration
statement in compliance with the Securities Act, and the declaration and
ordering by the SEC of effectiveness of such registration statement or document.

     "REGISTRABLE COMMON STOCK" means any Common Stock beneficially held or
acquired by Prentiss or his assigns (each a "HOLDER" and collectively, the
"HOLDERS") and any securities issued or issuable in respect thereof by way of
any stock split or stock dividend or in connection with any combination of
shares, recapitalization, merger, consolidation, reorganization or otherwise;
PROVIDED that Registrable Common Stock shall exclude Common Stock: (i) sold by a
Person in a transaction in which a Holder's rights under this Agreement are not
assigned under this Agreement; (ii) that has been sold to or through a broker or
dealer or underwriter in a public distribution or a public securities
transaction, (iii) has been sold in a transaction exempt from the Securities Act
under Section 4(1) thereof so that all transfer restrictions and restrictive
legends with respect thereto are removed upon the consummation of such sale,
(iv) that is able to be sold pursuant to Rule 144(k); or (v) that is held by a
Holder that does not "beneficially own" more than 1% of the outstanding Common
Stock and such Common Stock is able to be sold under Rule 144 (other than Rule
144(k)).

     "RULE 144" means Rule 144 under the Securities Act.

     "SEC" means the United States Securities and Exchange Commission.

     "SECURITIES ACT" means the Securities Act of 1933, as amended.

                                    SECTION 2
                               REGISTRATION RIGHTS

     The Holders shall have the right to register their Registrable Common
Stock in accordance with the following provisions:

     2.1 DEMAND REGISTRATION RIGHTS.

     (a) Upon receipt of a written request from Holders holding more than 30% of
the Registrable Common Stock to register under the Securities Act (whether for
purposes of a public offering, an exchange offer or otherwise) all or part of
the Registrable Common Stock held by such Holders, the Company shall as
expeditiously as reasonably practicable prepare and file (but not more than 30
days after receiving notice), and use its best efforts to cause to become
effective as soon thereafter as practicable, a registration statement on Form
S-1 or Form S-3 (including a shelf

                                       2
<PAGE>

registration statement under Rule 415) under the Securities Act to effect the
offering of such Registrable Common Stock in the manner specified in such
request.

     (b) Notwithstanding anything to the contrary contained elsewhere herein,
the registration rights granted to the Holders in SECTION 2.1(a) are subject to
the following terms and conditions:

          (i) Upon receipt of a request to register Registrable Common Stock
     pursuant to SECTION 2.1(a), the Company shall give all of the Holders
     prompt written notice of the proposed registration and will give all of
     such Holders the right to include their shares of Registrable Common Stock
     in such registration on the same terms and conditions as the requesting
     Holders. Each Holder so notified shall have ten days to request that their
     Registrable Common Stock be included in such registration. Failure to so
     request shall be deemed a waiver of such Holder's rights with respect to
     such registration unless such registration is not completed.

          (ii) The Holders will be limited to two registration requests under
     SECTION 2.1(a).

          (iii) The Company shall not be required to include a Holder's
     Registrable Common Stock in an offering unless such Holder accepts the
     terms of the underwriting agreement between the Company and the managing
     underwriter or underwriters and otherwise complies with SECTION 3.2. If the
     Holder accepts the terms of the underwriting agreement and otherwise
     complies with SECTION 3.2, then the securities to be included in such
     offering shall be allocated first to the Holders requesting registration of
     their Registrable Common Stock hereunder, and then, to the extent that any
     additional securities can, in the good faith judgment of such managing
     underwriter or underwriters, be sold without creating any such jeopardy to
     the success of such offering, among the Company and other Persons having
     the right to register securities in connection with such registration. To
     the extent it is impracticable to include all of the Registrable Common
     Stock requested to be included in such registration, then, subject to the
     priority of participation described above, the shares of Registrable Common
     Stock to be sold shall be allocated PRO RATA among each Person
     participating in the offering based upon the number of shares of Common
     Stock such Person requests to have included in such registration.

          (iv) The Company shall be entitled to defer for a reasonable period of
     time, but not in excess of 90 days and only one time in any twelve month
     period, the filing of any registration statement otherwise required to be
     prepared and filed by it under SECTION 2.1(a) if the Company furnishes the
     Holders a certified resolution of the Board within ten days after the
     Company has received the registration request under SECTION 2.1 that the
     Company (a) is at such time conducting or about to conduct an underwritten
     public offering of its securities for its own account and the Board
     determines in good faith that such offering would be materially adversely
     affected by such registration requested by the Holders or (b) would be
     required to disclose in such registration statement information not
     otherwise then required by law to be publicly disclosed and, in the good
     faith judgment of the Board, such disclosure might adversely affect any
     material business transaction or negotiation in which the Company is then
     engaged. If the Company elects

                                       3
<PAGE>

     to defer the filing of a registration statement pursuant to this SECTION
     2.1(b)(iv), the Holders shall be deemed to have withdrawn their request
     during the time of such deferral and shall retain their rights pursuant to
     SECTION 2.1(b)(ii).

          (v) If some but less than all of a Holder's shares of Registrable
     Common Stock are included in an offering contemplated by a registration
     statement pursuant to SECTION 2.1(a) and the offering is an underwritten
     offering, such Holder shall execute one or more reasonable and customary
     "lock-up" letters setting forth an agreement by such Holder not to offer
     for sale, sell, grant any option for sale of, or otherwise dispose of,
     directly or indirectly, any shares of Common Stock, for the greater of 60
     days or such other period as may be reasonably requested by an underwriter
     after the effective date of the underwritten offering.

          (vi) No demand for registration may be made under SECTION 2.1(a)
     within 180 days of the consummation of the last offering for which
     registration has been provided under SECTION 2.1(a).

     2.2 SHELF REGISTRATION. Notwithstanding anything contained herein, the
Company shall (i) file to register all of the Registrable Common Stock in
accordance with Rule 415 under the Securities Act and Section 3 of this
Agreement within 30 days after the effectiveness of the Merger and (ii) use
commercially reasonable efforts to obtain the effectiveness of the applicable
registration statement as soon as possible after filing and to maintain the
effectiveness of the registration statement pursuant to which such Registrable
Common Stock was registered until such securities have been sold. To the extent
the Company registers all of the Registrable Common Stock in accordance with
Rule 415 under the Securities Act and Section 3 of this Agreement within 180
days after the effectiveness of the Merger, maintains the effectiveness of the
registration statement pursuant to which such Registrable Common Stock was
registered until such securities have been sold, and otherwise satisfies its
obligations under this Agreement, no Holder shall be permitted to exercise the
registration rights set forth in Section 2.1 of this Agreement.

                                    SECTION 3
                                    COVENANTS

     3.1 COVENANTS OF THE COMPANY. In connection with any offering of shares of
Registrable Common Stock pursuant to this Agreement, the Company shall:

     (a) prepare and file with the Commission such amendments and post-effective
amendments to the registration statement as may be necessary to keep the
registration statement effective for a period of not less than 120 days (unless
filed pursuant to Rule 415 under the Securities Act, in which case such period
shall be until all such securities are sold), or such shorter period which will
terminate when all Registrable Common Stock covered by such registration
statement have been sold or withdrawn at the request of participating holders of
Common Stock and cause the prospectus to be supplemented by any required
prospectus supplement, and as so supplemented to be filed pursuant to Rule 424
under the Securities Act;

                                       4
<PAGE>

     (b) make available to each Holder and to each managing underwriter, if any,
(i) at least two business days prior to filing with the SEC, any registration
statement covering shares of Registrable Common Stock, any amendment or
supplement thereto, and any prospectus used in connection therewith, which
documents will be subject to the reasonable review of such Holders and such
underwriter, and, with respect to a registration statement prepared pursuant to
SECTION 2, the Company shall not file any such documents with the SEC to which
any such Holder shall reasonably object, and (ii) a copy of any and all
transmittal letters or other correspondence with the SEC or any other
governmental agency or self-regulatory body or other body having jurisdiction
(including any domestic or foreign securities exchange) relating to such
offering of shares of Registrable Common Stock;

     (c) furnish to each Holder and each managing underwriter, if any, such
number of copies of such registration statement, each amendment and supplement
thereto (in each case including all exhibits thereto and documents incorporated
by reference therein except to the extent available on the internet) and the
prospectus included in such registration statement (including each preliminary
prospectus and prospectus supplement) as such Holder or such underwriter may
reasonably request to facilitate the sale of the shares of Registrable Common
Stock;

     (d) after the filing of such registration statement, promptly notify each
Holder of any stop order issued or, to the Company's knowledge, threatened to be
issued by the SEC and promptly take all reasonable actions to prevent the entry
of such stop order or to obtain its withdrawal if entered;

     (e) use its commercially reasonable efforts to qualify such shares of
Registrable Common Stock for offer and sale under the securities, "blue sky" or
similar laws of such jurisdictions (including any foreign country or any
political subdivision thereof in which shares of Common Stock are then listed)
as any Holder or any underwriter shall reasonably request and use its
commercially reasonable efforts, to obtain all appropriate registrations,
permits and consents required in connection therewith, except that the Company
shall not for any such purpose be required to qualify generally to do business
as a foreign corporation in any jurisdiction where it is not so qualified, or to
subject itself to taxation or to file a general consent to service of process in
any such jurisdiction;

     (f) promptly inform each Holder (i) in the case of any offering of shares
of Registrable Common Stock in respect of which a registration statement is
filed under the Securities Act, of the date on which such registration statement
or any post-effective amendment thereto becomes effective and, if applicable, of
the date of filing a Rule 430A prospectus (and, in the case of an offering
abroad of shares of Registrable Common Stock, of the date when any required
filing under the securities and other laws of such foreign jurisdictions shall
have been made and when the offering may be commenced in accordance with such
laws), and (ii) of any request by the SEC, any securities exchange, government
agency, self-regulatory body or other body having jurisdiction for any amendment
of or supplement to any registration statement or preliminary prospectus or
prospectus included therein or any offering memorandum or other offering
document relating to such offering;

                                       5
<PAGE>

     (g) subject to SECTION 3.1(i), until the earlier of (i) such time as all of
the shares of Registrable Common Stock being offered have been disposed of in
accordance with the intended method of disposition by such Holder set forth in
the registration statement or other offering document (and the expiration of any
prospectus delivery requirements in connection therewith) and (ii) the
expiration of 120 days after such registration statement or other offering
document becomes effective (unless the offering is a continuous offering of
securities pursuant to Rule 415, in which case until the earliest of the date
the offering is completed and the second anniversary of the effective date
thereof; (PROVIDED HOWEVER, that if the effectiveness of such registration
statement is suspended for any reason, then the contemplated period shall extend
for the time such registration statement's effectiveness was suspended), keep
effective and maintain any registration, qualification or approval obtained in
connection with the offering of the shares of Registrable Common Stock, and
amend or supplement the registration statement or prospectus or other offering
document used in connection therewith to the extent necessary to comply with
applicable securities laws;

     (h) use its commercially reasonable efforts to have the shares of
Registrable Common Stock listed on any domestic and foreign securities exchanges
on which the Common Stock is then listed;

     (i) as promptly as practicable, notify each Holder at any time when a
prospectus relating to the sale of the shares of Registrable Common Stock is
required by law to be delivered in connection with sales by an underwriter or
dealer, of the occurrence of an event requiring the preparation of a supplement
or amendment to such prospectus so that, as thereafter delivered to the
purchasers of such shares, such prospectus will not contain an untrue statement
of a material fact or omit to state any material fact required to be stated
therein or necessary to make the statement therein, in light of the
circumstances under which they were made, not misleading, and as promptly as
practicable make available to each Holder and to each managing underwriter, if
any, any such supplement or amendment;

     (j) make available for inspection during the normal business hours of the
Company by any Holder, any underwriter participating in such offering, and any
attorney, accountant or other agent retained by any such Holder or any such
underwriter in connection with the sale of shares of Registrable Common Stock
(collectively, the "INSPECTORS"), all relevant financial and other records,
pertinent corporate documents and properties of the Company as shall be
reasonably necessary to enable them to exercise their due diligence
responsibility, and cause the officers, directors and employees of the Company
to supply all information reasonably requested by any such Inspector in
connection with such registration statement; provided, however, that (i) in
connection with any such inspection, any such Inspectors shall cooperate to the
extent reasonably practicable to minimize any disruption to the operation by the
Company of its business and (ii) any records, information or documents shall be
kept confidential by such Inspectors, unless (A) such records, information or
documents are in the public domain or otherwise publicly available or (B)
disclosure of such records, information or documents is required by a court or
administrative order or by applicable law and notice of such requirement is
promptly given to the Company after being received;

                                       6
<PAGE>

     (k) enter into usual and customary agreements (including an underwriting
agreement in usual and customary form) and take such other actions as are
reasonably required to expedite or facilitate the sale of the Registrable Common
Stock;

     (l) make "generally available to its security holders" (within the meaning
of Rule 158 under the Securities Act) an earnings statement satisfying the
provisions of Section 11(a) of the Securities Act and Rule 158 thereunder no
later than 45 days after the end of the 12-month period beginning with the first
day of the Company's first fiscal quarter commencing after the effective date of
the registration statement, which earnings statement shall cover said 12-month
period;

     (m) if requested by the managing underwriter or underwriters or the
Holders, promptly incorporate in a prospectus supplement or post-effective
amendment such information as the managing underwriter or underwriters or any
participating Holder, as the case may be, reasonably requests to be included
therein, including information with respect to the number of shares of
Registrable Common Stock being sold by the Holders to any underwriter or
underwriters, the purchase price being paid therefor by such underwriter or
underwriters and with respect to any other terms of an underwritten offering of
the Registrable Common Stock to be sold in such offering, and promptly make all
required filings of such prospectus by supplement or post-effective amendment;
and

     (n) take all other commercially reasonable steps necessary to effect the
registration of the Registrable Common Stock contemplated hereby.

     3.2 COVENANT OF HOLDERS. Each Holder agrees and covenants that, upon
receipt of any notice from the Company of the happening of any event of the kind
described in SECTION 3.1(i), such Holder will forthwith discontinue disposition
of Registrable Common Stock pursuant to the registration statement covering such
Registrable Common Stock until such Holder's receipt of the copies of the
supplemented or amended prospectus contemplated by SECTION 3.1(i), and, if so
directed by the Company, such Holder will deliver to the Company all copies,
other than permanent file copies, then in such Holder's possession of the most
recent prospectus covering such Registrable Securities at the time of receipt of
such notice.

                                    SECTION 4
              RESTRICTIONS ON PUBLIC SALE BY THE COMPANY AND OTHERS

     Unless required under a contract with another party, the Company agrees not
to effect any public sale or distribution of any securities during the 60-day
period commencing on the effective date of a registration statement with respect
to an underwritten offering filed pursuant to SECTION 2.1, except in connection
with any merger, acquisition, exchange offer, or any other business combination,
including any transaction within the scope of Rule 145 under the Securities Act,
subscription offer, dividend reimbursement plan or stock option or other
director or employee incentive or benefit plan.

                                       7
<PAGE>

                                    SECTION 5
                                    EXPENSES

     All expenses incurred in connection with the registration of Registrable
Common Stock, including all filing fees, escrow fees, fees and expenses of
compliance with securities or blue sky laws (including fees and disbursements,
if any, of the Company's counsel in connection with blue sky qualifications of
the Registrable Common Stock), rating agency fees, printing expenses, messenger
and delivery expenses, internal expenses (including all salaries and expenses of
the Company's officers and employees performing legal or accounting duties), the
fees and expenses incurred in connection with the listing of the securities to
be registered on each securities exchange on which similar securities issued by
the Company are then listed, and fees and disbursements of counsel for the
Company and the Company's independent certified public accountants (including
the expenses of any special audit or "cold comfort" letters required by or
incident to such performance) directly attributable to the registration of
securities, Securities Act liability insurance (if the Company elects to obtain
such insurance), the fees of counsel retained by a Holder and the fees and
expenses of any special experts or other Persons retained by the Company will be
borne by the Company. The Company shall have no obligation to pay and shall not
pay any underwriting fees, discounts or commissions in connection with any
Registrable Common Stock registered pursuant to this Agreement.

                                    SECTION 6
                                 INDEMNIFICATION

     6.1 INDEMNIFICATION BY THE COMPANY. The Company agrees to (a) indemnify and
hold harmless each Holder, its officers, directors and agents, and each Person,
if any, who controls any of the foregoing Persons within the meaning of either
Section 15 of the Securities Act or Section 20 of the Exchange Act, from and
against any and all losses, claims, damages and liabilities (individually, a
"LOSS"; collectively, "LOSSES") arising from or caused by (i) any untrue
statement or alleged untrue statement of a material fact contained in any
registration statement or prospectus relating to the Registrable Common Stock
(as amended or supplemented if the Company shall have furnished any amendments
or supplements thereto) or any preliminary prospectus, or caused by any omission
or alleged omission to state therein a material fact required to be stated
therein or necessary to make the statements therein not misleading, and (ii) any
violation or alleged violation by the Company of the Securities Act, any blue
sky laws, securities laws or other applicable laws of any state in which shares
of Registrable Common Stock are offered and relating to action or inaction
required of the Company in connection with such offering, and (b) reimburse each
such Person for any legal or other out-of-pocket expenses reasonably incurred in
connection with investigating, or defending against, any such Loss (or any
proceeding in respect thereof), subject to SECTION 6.3, except that the
indemnification provided for in this SECTION 6.1 shall not apply to Losses that
are caused by any such untrue statement or omission or alleged untrue statement
or omission based upon and in conformity with information furnished in writing
to the Company by or on behalf of any Holder expressly for use therein.
Notwithstanding the foregoing, the Company shall not be liable to the extent
that any such Loss arises out of, or is based upon, an untrue statement or
alleged untrue statement or omission or alleged omission made in any preliminary
prospectus if (i) a Holder failed to send or deliver a copy of the prospectus
included in the relevant registration statement at the time it became

                                       8
<PAGE>

effective (the "PROSPECTUS") with or prior to the delivery of written
confirmation of the sale of Registrable Common Stock to the Person asserting
such Loss or who purchased such Registrable Common Stock which are the subject
thereof if, in either case, such delivery is required by the Securities Act and
(ii) the Prospectus would have corrected such untrue statement or omission or
alleged untrue statement or alleged omission; and the Company shall not be
liable in any such case to the extent that any such Loss arises out of, or is
based upon, an untrue statement or alleged untrue statement of a material fact
or omission or alleged omission to state a material fact in the Prospectus, if
such untrue statement or alleged untrue statement or omission or alleged
omission is corrected in any amendment or supplement to the Prospectus and if,
having previously been furnished by or on behalf of the Company with copies of
the Prospectus as so amended or supplemented, a Holder thereafter fails to
deliver such Prospectus as so amended or supplemented prior to or concurrently
with the sale of Registrable Common Stock if such delivery is required by the
Securities Act.

     6.2 INDEMNIFICATION BY HOLDERS. Each Holder agrees to indemnify and hold
harmless the Company, its officers and directors, and each Person, if any, who
controls the Company within the meaning of either Section 15 of the Securities
Act or Section 20 of the Exchange Act to the same extent as the indemnity made
pursuant to SECTION 6.1 from the Company to such Holder, but only with reference
to information furnished in writing by or on behalf of such Holder expressly for
use in any registration statement or prospectus relating to shares of
Registrable Common Stock, or any amendment or supplement thereto, or any
preliminary prospectus.

     6.3 CONDUCT OF INDEMNIFICATION PROCEEDINGS. In case any proceeding
(including any governmental investigation) shall be instituted involving any
Person in respect of which indemnity may be sought pursuant to SECTION 6.1 OR
6.2, such Person (the "INDEMNIFIED PARTY") shall promptly notify the Person
against whom such indemnity may be sought (the "INDEMNIFYING PARTY") in writing,
provided, however, that the omission to so notify the Indemnifying Party will
not relieve the Indemnifying Party of any liability it may have under this
Agreement or otherwise except if such failure materially prejudices the
Indemnifying Party. The Indemnifying Party, upon the request of the Indemnified
Party, shall retain counsel reasonably satisfactory to such Indemnified Party
and shall pay the fees and disbursements of such counsel related to such
proceeding. In any such proceeding, any Indemnified Party shall have the right
to retain its own counsel, but the fees and expenses of such counsel shall be at
the expense of such Indemnified Party unless (a) the Indemnifying Party and the
Indemnified Party shall have mutually agreed to the retention, (b) the
Indemnifying Party shall have failed to comply with its obligations under the
preceding sentence or (c) the Indemnified Party shall have been advised by its
counsel in writing that actual interests exist between the Indemnifying Party
and the Indemnified Party. The Indemnifying Party shall not be liable for any
settlement of any proceeding effected without its written consent, which consent
shall not be unreasonably withheld. The Indemnifying Party shall not agree to
any settlement as the result of which any remedy or relief, other than monetary
damages for which the Indemnifying Party shall be fully responsible, shall be
applied to or against an Indemnified Party without the prior written consent of
the applicable Indemnified Party.

     6.4 CONTRIBUTION. If the indemnification provided for in SECTIONS 6.1 AND
6.2 from the Indemnifying Party is unavailable to an Indemnified Party in
respect of any Losses referred to therein, then the Indemnifying Party, in lieu
of indemnifying such Indemnified Party, shall

                                       9
<PAGE>

contribute to the amount paid or payable by such Indemnified Party as a result
of such Losses in such proportion to reflect the relative fault of the
Indemnifying Party and Indemnified Party in connection with the actions which
resulted in such Losses, as well as any other relevant equitable considerations.
The relative fault of such Indemnifying Party and Indemnified Party shall be
determined by reference to, among other things, whether any action in question,
including any untrue or alleged untrue statement of a material fact or omission
or alleged omission to state a material fact, has been made by, or relates to
information supplied by, such Indemnifying Party or Indemnified Party, and the
parties' relative intent, knowledge, access to information and opportunity to
correct or prevent such action. The amount paid or payable by a party as a
result of the Losses referred to above shall be deemed to include, subject to
the limitations set forth in SECTIONS 6.1 and 6.2, any legal or other fees or
expenses reasonably incurred by such party in connection with any investigation
or proceeding. No party shall be liable for contribution with respect to any
action or claim settled without its written consent, which consent shall not be
unreasonably withheld. Notwithstanding the provisions of this SECTION 6.4, no
Holder shall be required to contribute any amount in excess, if the amount of
the net proceeds such Holder received exceeds the amount of any Losses which
such Holder has otherwise been required to pay due to such untrue or alleged
untrue statement or omission of alleged omission. The parties hereto agree that
it would not be just and equitable if contribution pursuant to this SECTION 6.4
were determined by pro rata allocation or by any other method of allocation
which does not take into account the equitable considerations referred to in the
immediately preceding paragraphs. No Person guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Securities Act)
shall be entitled to contribution from any Person who was not guilty of such
fraudulent misrepresentation.

                                    SECTION 7
                                   TERMINATION

     So long as the Company has made the filings contemplated by ARTICLE 8 and,
as a result Holders may make resales of its Registrable Common Stock under Rule
144, this Agreement shall be suspended with respect to Holders that (i)
"beneficially own" less than 1% of the issued and outstanding Common Stock and
such Common Stock is able to be sold under Rule 144 (other than Rule 144(k)) or
(ii) are eligible to sell all of their Registrable Common Stock in accordance
with Rule 144(k). In addition, this Agreement shall terminate with respect to a
Holder if such Holder ceases to own any shares of Registrable Common Stock. For
this SECTION 7, a Holder shall be deemed to own any and all Common Stock such
Holder "beneficially owns" as such term is defined under Rule 13d-3 of the
Exchange Act. Notwithstanding the foregoing, the Company's and Holders' rights,
duties and obligations under SECTION 5, SECTION 6 and SECTION 8 shall survive
the termination or suspension of this Agreement.

                                    SECTION 8
                              AVAILABLE INFORMATION

     The Company shall take such reasonable actions and file such information,
documents and reports as shall be required by the SEC as a condition to the
availability of Rule 144 and Rule 144A, or any successor provisions.

                                       10
<PAGE>

                                    SECTION 9
                              ASSIGNMENT OF RIGHTS

     The rights of any Holder under this Agreement with respect to any
Registrable Common Stock owned by such Holder may be freely assigned to any
Holder who becomes the owner of at least 20% of the Registrable Common Stock
owned by such Holder as of the date hereof.

                                   SECTION 10
                                  MISCELLANEOUS

     10.1 PROVISION OF INFORMATION. Each Holder shall, and shall cause it
officers, directors, employees and agents to complete and execute all such
questionnaires as the Company shall reasonably request in connection with any
registration pursuant to this Agreement.

     10.2 INJUNCTIONS. Irreparable damage would occur if any provision of this
Agreement were not performed in accordance with its specified terms or were
otherwise breached. Therefore, the parties hereto shall be entitled to an
injunction or injunctions to prevent breaches of the provisions of this
Agreement and to enforce specifically the terms of provisions hereof in any
court having jurisdiction, such remedy being in addition to any other remedy to
which they may be entitled.

     10.3 SEVERABILITY. If any term or provision of this Agreement is held by a
court of competent jurisdiction to be unenforceable, the remainder of the terms
and provisions set forth herein shall remain in full force and effect and shall
in no way be affected, impaired or invalidated, and the parties hereto shall use
their best efforts to find and employ an alternative means to achieve the same
or substantially the same result as that contemplated by such term or provision.

     10.4 FURTHER ASSURANCES. Subject to the specific terms of this Agreement,
each Holder and the Company shall make, execute, acknowledge and deliver such
other instruments and documents, and take all such other actions, as may be
reasonably required to effectuate the purposes of this Agreement and to
consummate the transactions contemplated hereby.

     10.5 ENTIRE AGREEMENT; MODIFICATION. This Agreement and the Employment
Agreement contain the entire understanding of the parties with respect to the
transactions contemplated hereby and supersede all agreements and understandings
entered into prior to the execution hereof except as otherwise provided in the
Employment Agreement. This Agreement may be modified or provisions may be waived
hereunder only by a written instrument duly executed by or on behalf of the
Company and Holders who collectively own in excess of 50% of the Registrable
Common Stock.

     10.6 COUNTERPARTS. For the convenience of the parties hereto, any number of
counterparts of this Agreement may be executed by the parties hereto, but all
such counterparts shall be deemed one and the same instrument.

     10.7 NOTICES. All notices, consents, requests, demands, and other
communications hereunder shall be in writing and shall be given by hand or by
mail (return receipt requested) or

                                       11
<PAGE>

sent by overnight delivery service, cable, telegram, or facsimile transmission
to the parties at the address specified beside each party's name on the
signature pages hereto or at such other address as shall be specified by the
parties by like notice. Notice so given shall, in the case of notice so given by
mail, be deemed to be given and received on the fourth business day after
posting, in the case of notice so given by overnight delivery service, on the
day after notice is deposited with such service, and in the case of notice so
given by cable, telegram, facsimile transmission or, as the case may be,
personal delivery, on the date of actual delivery.

     10.8 GOVERNING LAW. THIS AGREEMENT IS GOVERNED BY THE LAWS OF THE STATE OF
TEXAS WITHOUT REGARD TO ANY CHOICE OF LAW OR CONFLICT OF LAW PRINCIPLES (WHETHER
OF THE STATE OF TEXAS OR ANY OTHER JURISDICTION) THAT WOULD CAUSE THE
APPLICATION OF THE LAWS OF ANY JURISDICTION OTHER THAN THE STATE OF TEXAS.

     10.9 SUCCESSORS AND ASSIGNS. This Agreement shall be binding upon and shall
inure to the benefit of and be enforceable by and against the successors and
permitted assigns of the parties hereto, including and without the need for an
express assignment, subsequent holders of Registrable Common Stock that are
permitted assigns pursuant to ARTICLE 9. Except as provided herein, the parties
may not assign their rights under this Agreement and the Company may not
delegate its obligations under this Agreement. Any attempted assignment or
delegation prohibited hereby shall be void.

     10.10 PARTIES IN INTEREST. Except as otherwise specifically provided
herein, nothing in this Agreement expressed or implied is intended or shall be
construed to confer any right or benefit upon any Person other than the Holders
and the Company and their respective successors and permitted assigns.

                            [SIGNATURE PAGE FOLLOWS]

                                       12
<PAGE>

     IN WITNESS WHEREOF, the Holder and the Company have caused this Agreement
to be duly executed as of the date first above written.

Address:                               _________________________________________
5006 Seneca Drive                      Michael V. Prentiss
Dallas, Texas 75209
214-350-3011

                                       MACK-CALI REALTY CORPORATION,
                                       a Maryland corporation

Address:                               By:______________________________________
11 Commerce Dr.                        Name:____________________________________
Cranford, New Jersey  07016            Title:___________________________________
908-272-8000<PAGE>

                                                                Exhibit 10.5

                            STOCK PURCHASE AGREEMENT

         This Stock Purchase Agreement (this "AGREEMENT") is made as of June 27,
2000 by and between Mitchell E. Hersh, an individual ("PURCHASER"), and Ampulla,
LLC, a Texas limited liability company (the "SELLER").

         WHEREAS, the Seller owns all of the outstanding voting capital stock
(the "SHARES") of Prentiss Properties Limited, Inc., a Delaware corporation (the
"COMPANY").

         WHEREAS, the Seller desires to sell to Purchaser, and the Purchaser
desires to purchase from the Seller, all of the Shares on the terms and subject
to the conditions contained herein.

         WHEREAS, the execution of this Agreement is a condition to and an
inducement for Mack-Cali Realty Corporation and Mack-Cali Realty, L.P. to enter
into that certain Agreement and Plan of Merger, dated as of the date hereof, by
and among Mack-Cali Realty Corporation, Mack-Cali Realty, L.P., Prentiss
Properties Trust and Prentiss Properties Acquisition Partners, L.P. (the "MERGER
AGREEMENT").

         NOW THEREFORE, in consideration of the premises and mutual covenants
and agreements set forth herein, the parties hereto agree as follows:

         1. SALE AND PURCHASE OF THE SHARES. At the Closing (as hereinafter
defined) and upon the terms and subject to the conditions of this Agreement, the
Seller shall sell, deliver and transfer to the Purchaser, and the Purchaser
shall purchase and acquire from the Seller, all right, title and interest in and
to the Shares. As consideration for the purchase of the Shares, Purchaser shall
pay to the Seller the sum of One Hundred and Twenty Five Thousand Dollars
($125,000) (the "PURCHASE PRICE"). The Purchase Price shall be paid at Closing
by wire transfer of immediately available funds.

         2. CLOSING DELIVERIES. Subject to the conditions contained in this
Agreement, the deliveries contemplated by SECTION 1 hereof shall occur at such
time and date as the Merger (as defined in the Merger Agreement) is effected
(the "CLOSING"). To effect the transfer of the Shares, at the Closing (a) the
Seller will deliver to the Purchaser all original stock certificates evidencing
the Shares, duly endorsed or accompanied by appropriate stock powers, and (b)
the Purchaser will deliver to the Seller the Purchase Price in the manner
contemplated in SECTION 1 hereof. The deliveries set forth above shall be
considered to have taken place simultaneously, and no delivery shall be deemed
to have been completed until all other deliveries have been completed.

         3. REPRESENTATIONS AND WARRANTIES OF THE SELLER. The Seller represents
and warrants to the Purchaser as follows:

            3.1. OWNERSHIP. The Seller is the record and beneficial owner of the
Shares, free and clear of all liens, security interests, pledges, claims,
liabilities and restrictions of any nature whatsoever.

                                       1
<PAGE>

            3.2. TITLE TO SHARES. The Purchaser shall acquire good and
marketable title to such Shares being purchased by such Purchaser from the
Seller free and clear of any liens, security interests, encumbrances and
restrictions of any nature whatsoever, except for restrictions imposed by
applicable federal and state securities laws.

            3.3. ORGANIZATION AND AUTHORITY. The Seller is a limited
liability company duly organized, validly existing and in good standing under
the laws of the State of Texas and has all requisite limited liability company
power and authority to enter into and perform this Agreement and to carry out
the transactions contemplated by this Agreement. The execution, delivery and
performance by the Seller of this Agreement and the consummation of the
transactions contemplated hereby by the Seller have been duly authorized by all
necessary company action on the part of the Seller. This Agreement has been duly
executed and delivered by the Seller and is a valid and binding obligation of
the Seller enforceable against the Seller in accordance with its terms, except
as such enforceability may be limited by bankruptcy, insolvency, reorganization,
moratorium and similar laws relating to or affecting creditors' rights generally
and by general equitable principles (regardless of whether such enforceability
is considered in a proceeding in law or in equity).

            3.4. NO CONFLICTS. The execution, delivery and performance of
this Agreement and the consummation of the transactions contemplated by this
Agreement do not and will not conflict with or result in any breach of any
terms, conditions or provisions of, or constitute a default, under (a) the
Seller's Articles of Organization or by-laws (each as amended to date and
presently in effect), (b) any agreement or other instrument to which the Seller
is a party or by which it or any of its properties is bound and which conflict,
breach or default would have a material adverse effect upon the Seller, its
assets, properties, business or condition (financial or otherwise) or (c) any
decree, judgment, order, statute, rule or regulation applicable to the Seller.

            3.5. NO CONSENTS. No consent, approval, order, authorization
or waiver from, notice to or declaration, registration or filing with any
governmental authority or any other person is necessary in connection with the
execution, delivery and performance by the Seller of this Agreement or the
consummation of the transactions contemplated hereby.

         4. REPRESENTATIONS AND WARRANTIES OF THE PURCHASER. The Purchaser
represents and warrants to the Seller as follows:

            4.1. ORGANIZATION AND AUTHORITY. This Agreement has been duly
executed and delivered by the Purchaser and is a valid and binding obligation of
the Purchaser enforceable against the Purchaser in accordance with its terms,
except as such enforceability may be limited by bankruptcy, insolvency,
reorganization, moratorium and similar laws relating to or affecting creditors'
rights generally and by general equitable principles (regardless of whether such
enforceability is considered in a proceeding in law or in equity).

            4.2. NO CONFLICTS. The execution, delivery and performance of
this Agreement and the consummation of the transactions contemplated by this
Agreement do not and will not conflict with or result in any breach of any of
the terms, conditions or provisions of, or constitute

                                       2
<PAGE>

a default under (a) any agreement or other instrument to which the Purchaser is
party or by which it or any of its properties is bound and which conflict,
breach or default would have a material adverse effect upon the Purchaser, its
assets, properties, business or condition (financial or otherwise) or (b) any
decree, judgment, order, statute, rule or regulation applicable to the
Purchaser.

            4.3. NO CONSENTS. No consent, approval, order, authorization
or waiver from, notice to or declaration, registration or filing with any
governmental authority or any other person is necessary in connection with the
execution, delivery and performance by the Purchaser of this Agreement or the
consummation of the transactions contemplated hereby.

            4.4. ACCESS TO INFORMATION. The Purchaser has received or has
had full access to all the information it considers necessary or appropriate to
make an informed decision with respect to the Shares to be purchased by such
Purchaser under this Agreement. The Purchaser has had an opportunity to ask
questions and receive answers from the Company and the Seller regarding the
terms and conditions of the purchase of the Shares and to obtain additional
information (to the extent the Company or the Seller possessed such information
or could acquire it without unreasonable effort or expense) necessary to verify
any information furnished to such Purchaser or to which such Purchaser has had
access.

            4.5. INVESTMENT REPRESENTATIONS. The Purchaser understands
that the Shares have not been registered under the Securities Act of 1933, as
amended. The Purchaser is acquiring the Shares for investment purposes only and
is not purchasing the Shares with a view to the sale or distribution of any part
thereof. The Purchaser has made such investigation into the Company that
Purchaser considers necessary and appropriate to its purchase of the Shares, is
capable of evaluating the merits and risks of its purchase of the Shares, and is
relying solely upon such investigation and not upon any representation or
warranty made by Seller or the Company, other than the representations and
warranties specifically made in this Agreement.

         5. TERMINATION. This Agreement shall be terminated upon the occurrence
of any of the following circumstances:

         (a) By mutual written agreement of the Seller and the Purchaser; or

         (b) Upon the termination of the Merger Agreement in accordance with its
terms.

         6.  MISCELLANEOUS.

             6.1. NOTICES. All notices, consents and other communications
required or permitted under this Agreement shall be in writing, and shall be
deemed to have been duly given (a) when delivered personally, (b) when
received if sent by first class certified mail, postage prepaid, return
receipt requested, or (c) when delivered by an internationally recognized
overnight delivery service, postage or delivery charges prepaid, to a party.
Notices may also be given by facsimile and shall be effective on the date
transmitted if confirmed within twenty-four (24) hours thereafter by a signed
original sent in the manner provided in the preceding sentence. Any party may
change its address for notices by giving notice of a new address to the other
party in accordance with this SECTION 6.1, except that any such change of
address notice shall not be

                                       3
<PAGE>

effective unless and until received. Any notice shall be sent to the parties
at the addresses set forth below:

                  If to the Seller:

                  Ampulla, L.L.C.
                  Michael V. Prentiss
                  5006 Seneca
                  Dallas, Texas 75209
                  Fax Number: (214) 351-5006

                  With a copy to:

                  Akin, Gump, Strauss, Hauer & Feld, L.L.P.
                  1700 Pacific Avenue, Suite 4100
                  Dallas, Texas 75201
                  Fax Number:  (214) 969-4343
                  Attn.:  Michael E. Dillard, P.C.

                  If to the Purchaser:

                  Mitchell E. Hersh
                  Mack-Cali Realty Corporation
                  11 Commerce Drive
                  Cranford, New Jersey  07016
                  Fax Number: (908) 272-6755

                  With a copy to:

                  Pryor, Cashman, Sherman & Flynn, LLP
                  410 Park Avenue
                  New York, New York  100222
                  Fax Number: (212) 326-0806
                  Attn.:  Blake Hornick, Esq.

             6.2. ENTIRE AGREEMENT. This Agreement constitutes the entire
agreement of the parties with respect to the subject matter hereof and
supersedes any and all prior written or oral communications and agreements, and
all contemporaneous oral communications among the parties concerning the subject
matter hereof.

             6.3. AMENDMENTS. No provision of this Agreement may be
amended, changed or modified in any manner, orally or otherwise, except by an
instrument in writing signed by the parties affected by such provision.

             6.4. SUCCESSORS AND ASSIGNS. This Agreement shall be binding
upon and inure to the benefit of the parties and their respective beneficiaries,
heirs, executors, administrators,

                                       4
<PAGE>

successors and assigns. No party shall in any manner assign any of its rights or
obligations under this Agreement without the prior written consent of the other
party.

             6.5. GOVERNING LAW. THIS AGREEMENT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS, WITHOUT GIVING
EFFECT TO PRINCIPLES OF CONFLICTS OF LAW OF ANY JURISDICTION.

             6.6. COUNTERPARTS. This Agreement may be executed in two or
more counterparts, each of which shall be deemed an original but all of which
together shall constitute one and the same instrument.

             6.7. SURVIVAL OF REPRESENTATIONS AND WARRANTIES. All
representations and warranties contained herein shall survive the execution and
delivery of this Agreement and the Closing hereof, regardless of any
investigation at any time made by or on behalf of any party hereto.

             6.8. FURTHER ASSURANCES. At the Closing and thereafter, from
time to time and without additional consideration, the Seller and the Purchaser,
as the case may be, shall execute and deliver, or cause to be executed and
delivered, such additional or further transfers, assignments, endorsements,
consents and other instruments as the Purchaser or the Seller, as the case may
be, may reasonably request for the purpose of effectively carrying out the
transactions contemplated by this Agreement.

                            [SIGNATURE PAGE FOLLOWS]

                                       5
<PAGE>

         IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date first above written.

                                       SELLER:

                                       AMPULLA, L.L.C.

                                       By: /s/ Michael V. Prentiss
                                       -----------------------------
                                       Michael V. Prentiss
                                       Sole Member

                                       PURCHASER:

                                       /s/ Mitchell E. Hersh
                                       -----------------------------
                                       Mitchell E. Hersh

                                       6

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