<SUBMISSION>
<ACCESSION-NUMBER>0000912057-00-000712
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>19991213
<FILING-DATE>20000110
<SUBJECT-COMPANY>
<COMPANY-DATA>
<CONFORMED-NAME>MACK CALI REALTY CORP
<CIK>0000924901
<ASSIGNED-SIC>6798
<IRS-NUMBER>223305147
<STATE-OF-INCORPORATION>MD
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-13274
<FILM-NUMBER>504620
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>11 COMMERCE DR
<STREET2>1ST FLOOR
<CITY>CRANFORD
<STATE>NJ
<ZIP>07016
<PHONE>9082728000
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>11 COMMERCE DRIVE
<STREET2>1ST FLOOR
<CITY>CRANFORD
<STATE>NJ
<ZIP>07016
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>CALI REALTY CORP /NEW/
<DATE-CHANGED>19960730
</FORMER-COMPANY>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>CALI REALTY L P
<DATE-CHANGED>19941025
</FORMER-COMPANY>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>CALI REALTY CORP
<DATE-CHANGED>19940608
</FORMER-COMPANY>
</SUBJECT-COMPANY>
<REPORTING-OWNER>
<COMPANY-DATA>
<CONFORMED-NAME>BYRNE BRENDAN T
<CIK>0000751250
<ASSIGNED-SIC>
<RELATIONSHIP>DIRECTOR
</COMPANY-DATA>
<FILING-VALUES>
<FORM-TYPE>4
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>MACK CALI REALTY CORP
<STREET2>11 COMMERCE DR
<CITY>CRANFORD
<STATE>NJ
<ZIP>07016
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>MACK CALI REALTY CORP
<STREET2>11 COMMERCE DR
<CITY>CRANFORD
<STATE>NJ
<ZIP>07016
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<DESCRIPTION>FORM 4
<TEXT>

<PAGE>

<TABLE>
<CAPTION>
--------                                      U.S. SECURITIES AND EXCHANGE COMMISSION
 FORM 4                                                Washington, D.C. 20549
--------
/ / CHECK THIS BOX IF NO                    STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP
    LONGER SUBJECT TO
    SECTION 16.  FORM 4 OR    Filed pursuant to Section 16(a) of the Securities and Exchange Act of 1934,
    FORM 5 OBLIGATIONS MAY       Section 17(a) of the Public Utility Holding Company Act of 1935 or
    CONTINUE.                            Section 30(f) of the Investment Company Act of 1940
    SEE INSTRUCTION 1(b).
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<S>                                          <C>                                             <C>
1. Name and Address of Reporting Person*     2. Issuer Name and Ticker or Trading Symbol     6. Relationship of Reporting Person(s)
                                                                                                 to Issuer (Check all applicable)
                                                                                               __X_ Director        ____ 10% Owner
   Byrne           Brendan          T.          Mack-Cali Realty Corporation (CLI)
---------------------------------------------------------------------------------------------  ____ Officer (give   ____ Other
   (Last)          (First)        (Middle)   3. IRS or Social Security  4. Statement for                     title       (specify
                                                Number of Reporting        Month/Year                        below)       below
                                                Person (Voluntary)                            -----------------  ------------------
  c/o Mack-Cali Realty Corporation
  11 Commerce Drive                                                           12/99
--------------------------------------------                            --------------------- 7. Individual or Joint/Group Filing
                  (Street)                                              5. If Amendment,          (Check Applicable Line)
                                                                           Date of Original   _X_Form filed by One Reporting Person
   Cranford, New Jersey 07016                                              (Month/Year)       ___Form filed by More than One
--------------------------------------------                                                     Reporting Person
   (City)       (State)            (Zip)

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                                               TABLE I - NON-DERIVATIVE SECURITIES ACQUIRED, DISPOSED OF, OR BENEFICIALLY OWNED
------------------------------------------------------------------------------------------------------------------------------------
1. Title of Security               2. Trans-   3. Trans-     4. Securities Acquired (A)    5. Amount of     6. Owner-   7. Nature
   (Instr. 3)                         action      action        or Disposed of (D)            Securities       ship        of In-
                                      Date        Code          (Instr. 3, 4 and 5)           Beneficially     Form:       direct
                                      (Month/    (Instr. 8)                                   Owned at         Direct      Bene-
                                       Day/                                                   End of           (D) or      ficial
                                       Year)   -------------------------------------------    Month            Indirect    Owner-
                                                Code    V       Amount    (A) or              (Instr. 3        (I)         ship
                                                                          (D)     Price       and 4)           (Instr. 4) (Instr. 4)
------------------------------------------------------------------------------------------------------------------------------------
Common Stock                       12/13/99      P              500        A      $24.187     600               I          By wife
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* If the form is filed by more than one reporting person, SEE Instruction 4(b)(v).
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.                   (Over)

</TABLE>

<PAGE>

<TABLE>
<CAPTION>

FORM 4 (CONTINUED)          TABLE II - DERIVATIVE SECURITIES ACQUIRED, DISPOSED OF, OR BENEFICIALLY OWNED
                                   (E.G., PUTS, CALLS, WARRANTS, OPTIONS, CONVERTIBLE SECURITIES)
------------------------------------------------------------------------------------------------------------------------
<S>                                 <C>          <C>         <C>           <C>                      <C>
1. Title of Derivative Security     2. Conver-   3. Trans-   4. Transac-   5. Number of Deriv-      6. Date Exer-
   (Instr. 3)                          sion or      action      tion Code     ative Securities Ac-     cisable and Ex-
                                       Exercise     Date        (Instr. 8)    quired (A) or Dis-       piration Date
                                       Price of    (Month/                    posed of (D)             (Month/Day/
                                       Deriv-       Day/                      (Instr. 3, 4, and 5)     Year)
                                       ative        Year)
                                       Security

                                                             ----------------------------------------------------------
                                                              Code    V        (A)        (D)        Date      Expira-
                                                                                                     Exer-     tion
                                                                                                     cisable   Date
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<CAPTION>

------------------------------------------------------------------------------------------
<S>                                 <C>        <C>           <C>            <C>
7. Title and Amount of Under-       8. Price   9. Number     10. Owner-     11. Nature
   lying Securities                    of         of Deriv-      ship           of In-
   (Instr. 3 and 4)                    Deriv-     ative          Form           direct
                                       ative      Securi-        of De-         Bene-
                                       Secur-     ties           rivative       ficial
                                       ity        Bene-          Secu-          Own-
                                       (Instr.    ficially       rity:          ership
                                       5)         Owned          Direct         (Instr. 4)
-------------------------------                   at End         (D) or
       Title         Amount or                    of             Indi-
                     Number of                    Month          rect (I)
                     Shares                       (Instr. 4)     (Instr. 4)

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Explanation of Responses:






                                                                                        /s/ Brendan T. Byrne             1/10/00
                                                                                  -----------------------------------  -----------
**Intentional misstatements or omissions of facts constitute                        **Signature of Reporting Person       Date
  Federal Criminal Violations.  SEE 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed.
      If space is insufficient, SEE Instruction 6 for procedure.

                                                                                                                              Page 2

</TABLE>

</TEXT>
</DOCUMENT>
</SUBMISSION>
