
<PAGE>


                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549


                                    FORM 8-K
                                 CURRENT REPORT

                         PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

                Date of report (date of earliest event reported):

                                  MARCH 7, 2000


                          MACK-CALI REALTY CORPORATION
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             (Exact name of Registrant as specified in its charter)


                                    Maryland
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                 (State or other jurisdiction of incorporation)


      1-13274                                                    22-3305147
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(Commission File No.)                                         (I.R.S. Employer
                                                             Identification No.)


                  11 Commerce Drive, Cranford, New Jersey 07016
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               (Address of Principal Executive Offices) (Zip Code)


                                 (908) 272-8000
                                 --------------
              (Registrant's telephone number, including area code)


                                       N/A
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          (Former Name or Former Address, if Changed Since Last Report)

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ITEM 5. OTHER EVENTS

     On June 10, 1999, the Board of Directors of Mack-Cali Realty Corporation
(the "Company") authorized a dividend distribution (the "Distribution") of one
preferred share purchase right (a "Right") for each outstanding share of common
stock, par value $0.01 per share (the "Common Shares"), of the Company. The
dividend was payable on July 6, 1999 (the "Record Date"), to the stockholders of
record on that date. Each Right entitles the registered holder to purchase from
the Company one one-thousandth (1/1000) of a share of Series A Junior
Participating Preferred Stock, par value $.01 per share (the "Preferred
Shares"), of the Company at a price of $100.00 per one one-thousandth of a
Preferred Share (the "Purchase Price"), subject to adjustment.

     The Company entered into a Shareholder Rights Agreement (the "Original
Rights Agreement") dated as of July 6, 1999, with ChaseMellon Shareholder
Services, LLC, a New Jersey limited liability company (the "ChaseMellon"),
pursuant to which, among other things, the Company appointed ChaseMellon as the
Rights Agent, as such term is defined in the Original Rights Agreement, to act
as the agent for the Company in accordance with the terms and conditions of the
Original Rights Agreement.

     The Company, EquiServe Trust Company, N.A, a Delaware corporation
("Equiserve"), ChaseMellon and The Chase Manhattan Bank entered into an
Agreement dated as of January 1, 2000, pursuant to which the parties, among
other things, amended the Original Rights Agreement to reflect the replacement
by the Company of ChaseMellon with EquiServe as the Rights Agent, effective as
of the close of business on November 21, 1999.

     The description and terms of the Rights are set forth in the Amended and
Restated Shareholder Rights Agreement (the "Amended and Restated Shareholder
Rights Agreement"), dated as of March 7, 2000, by and between the Company and
Equiserve, as Rights Agent.

     Initially, the Rights will be attached to all Common Shares certificates
representing shares then outstanding, and no separate Rights certificates will
be distributed. The Rights will separate from the Common Shares and a
Distribution Date will occur upon the earlier of (i) ten calendar days following
the date (the "Shares Acquisition Date") of public announcement that a person or
group of affiliated or associated persons (an "Acquiring Person") has acquired,
or obtained the right to acquire, beneficial ownership of fifteen percent (15%)
or more of the outstanding Common Shares or (ii) ten calendar days (or such
later date as may be determined by action of the Board of Directors prior to the
time any person or group of affiliated persons becomes an Acquiring Person)
following the commencement of, or public announcement of an intent to commence,
a tender offer or exchange offer the consummation of which would result in the
beneficial ownership by a person or group of fifteen percent (15%) or more of
the outstanding Common Shares (the earlier of such dates being called the
"Distribution


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Date"). Until the Distribution Date, the Rights will be evidenced by the Common
Share certificates and will be transferred with and only with such Common Share
certificates. New Common Share certificates issued after the Record Date will
contain a notation incorporating the Amended and Restated Shareholder Rights
Agreement by reference. Until the Distribution Date, the surrender for transfer
of any certificates representing outstanding Common Shares also will transfer
the Rights associated with the Common Shares represented by such certificate.
Any person or group owning in excess of 15% of the outstanding Common Shares as
of July 6, 1999, shall only trigger the effects referred to above if such person
increases its ownership of Common Shares to 10% or more greater than the
beneficial ownership of Common Shares of such Person on such date.

     As soon as practicable following the Distribution Date, separate
certificates representing the Rights ("Right Certificates") will be mailed to
holders of record of the Common Shares as of the close of business on the
Distribution Date and such separate Right Certificates alone will represent the
Rights.

     The Rights are not exercisable until the Distribution Date. The Rights will
expire at the close of business on July 6, 2009 (the "Final Expiration Date"),
unless the Final Expiration Date is extended or the Right Certificates are
earlier redeemed or exchanged by the Company, as described below. Each Right
generally will entitle the holder to purchase one one-thousandth (1/1,000th) of
a Preferred Share of the Company at a price of $100.00.

     In the event that, following the Distribution Date, any person or group
becomes an Acquiring Person, each holder of a Right will thereafter have the
right to receive, upon exercise, Common Shares having a market value equal to
two times the Purchase Price of the Right. Notwithstanding any of the foregoing,
once any person or group becomes an Acquiring Person, all Rights that are or
were beneficially owned by any such Acquiring Person will be null and void.

     For example, at an exercise price of $100.00 per Right, each Right not
owned by an Acquiring Person would entitle its holder to purchase $200.00 worth
of Common Stock for $100.00. Assuming that the Common Stock had a per share
value of $40.00 on the date upon which such person or group became an Acquiring
Person, the holder of each valid right would be entitled to purchase five (5)
shares of Common Stock for $100.00.

     In the event that, following the Distribution Date, (i) the Company is
acquired in a merger or other business combination transaction in which the
Company is not the surviving corporation, or (ii) 50% or more of the Company's
consolidated assets or earning power is sold or transferred, then each holder of
a Right (except Rights which previously have been voided as set forth in the
preceding paragraph) shall thereafter have the right to receive, upon exercise,
common stock of the acquiring company having a value equal to two times the
Purchase Price of the Right.


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     The Purchase Price payable, and the number of Preferred Shares (or Common
Shares) issuable, upon exercise of the Rights are subject to adjustment from
time to time to prevent dilution (i) in the event of a stock dividend on, or a
subdivision, combination or reclassification of, the Preferred Shares, (ii) upon
the grant to holders of the Preferred Shares of certain rights or warrants to
subscribe for the purchase of Preferred Shares or convertible securities at less
than the current market price of the Preferred Shares or (iii) upon the
distribution to holders of the Preferred Shares of evidences of indebtedness or
assets (excluding regular quarterly cash dividends or dividends payable in
Preferred Shares) or of subscription rights or warrants (other than those
referred to above).

     With certain exceptions, no adjustment in the Purchase Price will be
required until the time at which cumulative adjustments require an adjustment of
at least 1% in such Purchase Price. No fractional Preferred Shares will be
issued (other than fractional shares which are integral multiples of one
one-thousandth of a Preferred Share) and, in lieu thereof, an adjustment in cash
will be made based on the market price of the Preferred Shares on the last
trading date prior to the date of exercise.

     At any time after any person or group becomes an Acquiring Person, the
Board of Directors may cause the Company to exchange the Rights (other than
Rights owned by the Acquiring Person which shall have become void), in whole or
in part, at an exchange ratio of one Common Share per Right (subject to
adjustment).

     At any time prior to the earlier of (i) the close of business on the tenth
calendar day following the Shares Acquisition Date (or if the Shares Acquisition
Date shall have occurred prior to the Record Date, the close of business on the
tenth day following the Record Date) or (ii) the Final Expiration Date, the
Board of Directors of the Company may cause the Company to redeem the Rights in
whole, but not in part, at a price of $.0l per Right (the "Redemption Price").
Immediately upon the action of the Board of Directors of the Company electing to
redeem the Rights, the Company shall make announcement thereof, and upon such
action, the right to exercise the Rights will terminate and the only right of
the holders of Rights will be to receive the Redemption Price.

     Until a Right is exercised or exchanged, the holder thereof, as such, will
have no rights as a stockholder of the Company, including, without limitation,
the right to vote or to receive dividends.

     The terms of the Rights may be amended by the Board of Directors of the
Company without the consent of the holders of the Rights, including an amendment
to lower certain thresholds described above to not less than the greater of (i)
the sum of one one-thousandth percent (.001%) and the largest percentage of the
outstanding Common Shares then known to the Company to be beneficially owned by
any person or group (other than Acquiring Persons) and (ii) ten percent (10%),
except that from and after such time as any person or group becomes an Acquiring
Person no such amendment may adversely affect the interests of the holders of
the Rights.


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     The foregoing description of the Rights is qualified in its entirety by
reference to the Amended and Restated Shareholder Rights Agreement which is
attached as an exhibit to this Form 8-K.

     In connection with the foregoing, the Company hereby files the documents
listed below:

     Exhibit                  Document
     -------                  --------

     4.1                 Amended and Restated Shareholder Rights
                         Agreement, dated as of March 7, 2000,
                         between Mack-Cali Realty Corporation and
                         Equiserve Trust Company, N.A., as Rights
                         Agent
















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                                   SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.

                                   MACK-CALI REALTY CORPORATION


Date:  March 25, 2000              By: /s/ Barry Lefkowitz
                                       -------------------------------------
                                       Barry Lefkowitz
                                       Executive Vice President and
                                       Chief Financial Officer









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                                  EXHIBIT INDEX


     Exhibit                  Document
     -------                  --------

     4.1                 Amended and Restated Shareholder Rights
                         Agreement, dated as of March 7, 2000,
                         between Mack-Cali Realty Corporation and
                         Equiserve Trust Company, N.A., as Rights
                         Agent


















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