EXHIBIT 99.1

FIRST QUARTER 2004
Supplemental Operating and Financial Data

        This Supplemental Operating and Financial Data is not an offer to sell or solicitation to buy any securities of the Company. Any offers to sell or solicitations of the Company shall be made by means of a prospectus. The information in this Supplemental Package must be read in conjunction with, and is modified in its entirety by, the Quarterly Report on Form 10-Q (the "10-Q") filed by the Company for the same period with the Securities and Exchange Commission (the "SEC") and all of the Company's other public filings with the SEC (the "Public Filings"). In particular, the financial information contained herein is subject to and qualified by reference to the financial statements contained in the 10-Q, the footnotes thereto and the limitations set forth therein. Investors may not rely on the Supplemental Package without reference to the 10-Q and the Public Filings. Any investors' receipt of, or access to, the information contained herein is subject to this qualification.

INDEX

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Supplemental Operating and Financial Data for the Quarter Ended March 31, 2004

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DISCLOSURE REGARDING FORWARD-LOOKING STATEMENTS

        Certain information discussed in this literature may constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 and the federal securities laws, including Section 21E of the Securities Exchange Act of 1934. The Company intends such forward-looking statements to be covered by the safe harbor provisions for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995 and Section 21E of the Securities Exchange Act of 1934. Such forward-looking statements relate to, without limitation, the Company's future economic performance, plans and objectives for future operations and projections of revenue and other financial items. Forward-looking statements can be identified by the use of words such as "may," "will," "should," "expect," "anticipate," "estimate," "continue" or comparable terminology. Although the Company believes that the expectations reflected in such forward-looking statements are based upon reasonable assumptions at the time made, it can give no assurance that its expectations will be achieved. Forward-looking statements are inherently subject to certain risks, trends and uncertainties, many of which the Company cannot predict with accuracy and some of which the Company might not even anticipate. Future events and actual results, financial and otherwise, may differ materially from the results discussed in the forward-looking statements. Readers are cautioned not to place undue reliance on these forward-looking statements. Among the risks, trends and uncertainties are changes in the general economic conditions, including those affecting industries in which the Company's principal tenants compete; any failure of the general economy to recover timely from the current economic downturn; the extent of any tenant bankruptcies; the Company's ability to lease or re-lease space at current or anticipated rents; changes in the supply of and demand for office, office/flex and industrial/warehouse properties; changes in interest rate levels; changes in operating costs; the Company's ability to obtain adequate insurance, including coverage for terrorist acts; the availability of financing; and other risks associated with the development and acquisition of properties, including risks that the development may not be completed on schedule, that the tenants will not take occupancy or pay rent, or that development or operating costs may be greater than anticipated. For further information on factors which could impact the Company and the statements contained herein, reference should be made to the Company's filings with the Securities and Exchange Commission including Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and Annual Reports on Form 10-K. The Company assumes no obligation to update or supplement forward-looking statements that become untrue because of subsequent events.

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I. COMPANY BACKGROUND

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I.    COMPANY BACKGROUND

About the Company

        Mack-Cali Realty Corporation (NYSE: CLI) is one of the largest real estate investment trusts (REITs) in the United States with a total market capitalization of $4.9 billion at March 31, 2004. Mack-Cali has been involved in all aspects of commercial real estate development, management and ownership for over 50 years and has been a publicly-traded REIT since 1994. Mack-Cali owns or has interests in 263 properties, primarily class A office and office/flex buildings, totaling approximately 28.3 million square feet, serving as home to approximately 2,100 tenants. The properties are located primarily in suburban markets of the Northeast, many with adjacent, Company-controlled developable land sites able to accommodate up to 8.3 million square feet of additional commercial space.

History

        Established over 50 years ago, in 1994 the New Jersey-based firm became a publicly-traded company listed on the New York Stock Exchange under the ticker symbol CLI. Through combinations with some of the top companies in the real estate industry—most notably New Jersey-based Mack Company and Westchester, New York-based Robert Martin Company—Mack-Cali has become one of the leading real estate companies in the country.

Strategy

        Mack-Cali's strategy is to be a significant real estate owner and operator in its core, high-barriers-to-entry markets, primarily in the Northeast.

Summary
(as of March 31, 2004)

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Board of Directors

William L. Mack, Chairman of the Board

Executive Officers

        Mitchell E. Hersh, Chief Executive Officer

        Timothy M. Jones, President

        Barry Lefkowitz, Executive Vice President and Chief Financial Officer

        Roger W. Thomas, Executive Vice President, General Counsel and Secretary

        Michael A. Grossman, Executive Vice President

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Equity Research Coverage

Company Contact Information

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II. FINANCIAL HIGHLIGHTS

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II. FINANCIAL HIGHLIGHTS

Quarterly Summary

        Net income available to common shareholders for the first quarter 2004 equaled $26.3 million, or $0.44 per share, versus $30.0 million, or $0.52 per share, for the same quarter last year.

        Funds from operations (FFO) available to common shareholders for the quarter ended March 31, 2004 amounted to $64.9 million, or $0.87 per share, versus $69.0 million, or $0.97 per share, for the quarter ended March 31, 2003.

        Total revenues for the first quarter 2004 decreased 1.0 percent to $145.9 million as compared to $147.3 million for the same quarter last year.

        All per share amounts presented above are on a diluted basis.

        The Company had 60,401,346 shares of common stock, 10,000 shares of cumulative redeemable perpetual preferred stock, 7,789,498 common operating partnership units and 215,018 $1,000-face-value preferred operating partnership units outstanding as of March 31, 2004.

        The outstanding preferred units are convertible into 6,205,425 common operating partnership units. Assuming conversion of all preferred units into common units, the Company had a total of 74,396,269 shares/common units outstanding at March 31, 2004.

        As of March 31, 2004, the Company had total indebtedness of approximately $1.6 billion, with a weighted average annual interest rate of 6.71 percent. Mack-Cali had a total market capitalization of $4.9 billion and a debt-to-undepreciated assets ratio of 36.6 percent at March 31, 2004. The Company had an interest coverage ratio of 3.22 times for the quarter ended March 31, 2004.

        The following is a summary of the Company's recent activity:

Acquisitions

        In April, the Company acquired 5 Wood Hollow Road, a three-story, 317,040 square-foot class A office property located in Parsippany, New Jersey. The building was purchased for approximately $34 million. The acquisition of 5 Wood Hollow Road, which is 100 percent leased to Lucent Technologies, increases the Company's holdings in Parsippany to 14 buildings totaling 2.2 million square feet.

Financing Activity

        In January, the Company through its operating partnership, sold $100 million of 10-year senior unsecured notes. The 5.125 percent notes are due February 15, 2014. The proceeds from the issuance of approximately $98.5 million were applied to the repayment of 7-percent, $300 million face amount unsecured notes at maturity on March 15, 2004.

        In March, the Company through its operating partnership, re-opened and sold an additional $100 million of 10-year 5.125 percent senior unsecured notes due February 15, 2014. The proceeds from the issuance of approximately $103.2 million were used primarily to reduce outstanding borrowings under the Company's credit facility.

        Also in March, the Company's Board of Directors declared a cash dividend of $0.63 per common share (indicating an annual rate of $2.52 per common share) for the first quarter 2004, which was paid on April 19, 2004 to shareholders of record as of April 5, 2004. The Board also declared a cash dividend of $0.50 per depositary share, each representing 1/100^th of a share of 8-percent Series C cumulative redeemable perpetual preferred stock ($25 liquidation value per depositary share) for the period January 15, 2004 through April 14, 2004. The preferred stock dividend was paid on April 15, 2004 to shareholders of record as of April 5, 2004.

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Leasing Information

        Mack-Cali's consolidated in-service portfolio was 91.1 percent leased at March 31, 2004, compared to 91.5 percent leased at December 31, 2003.

        For the quarter ended March 31, 2004, the Company executed 151 leases totaling 727,337 square feet, consisting of 563,319 square feet of office space, 147,118 square feet of office/flex space, 7,600 square feet of industrial/warehouse space and 9,300 square feet at one of the Company's stand-alone retail properties. Of these totals, 274,343 square feet were for new leases and 452,994 square feet were for lease renewals and other tenant retention transactions.

        Highlights of the quarter's leasing transactions included:

•

Deloitte & Touche USA, LLP renewed its lease for 88,170 square feet for three years at Two Hilton Court in Parsippany, New Jersey. The 181,592 square-foot class A office building, which is located in the Mack-Cali Business Campus, is 89.8 percent leased.



•

AFP Imaging Corporation, a manufacturer of medical and veterinary x-ray equipment, signed a one-year renewal for 47,735 square feet at 250 Clearbrook Road in Elmsford, New York. The 155,000 square-foot office/flex building is located in the Cross Westchester Executive Park and is 94.5 percent leased.



•

CPG Partners, LP, an affiliate of Chelsea Property Group, Inc., signed a new, 10-year lease for 43,589 square feet at 105 Eisenhower Parkway in Roseland, New Jersey. The 220,000 square-foot class A office property, which is located in the Eisenhower/280 Corporate Center, is 83.4 percent leased.



•

Greater New York Mutual Insurance Company, a property and casualty insurer, renewed its lease for 100 percent of the 40,000 square-foot office building located at 377 Summerhill Road in East Brunswick, New Jersey for five years.



•

Allstate Insurance Company executed a five-year renewal of its lease for 25,497 square feet at 224 Strawbridge Drive in Moorestown, New Jersey. The 74,000 square-foot class A office building is 100 percent leased.



•

PNC Bank N.A. renewed its lease for 23,337 square feet at 1000 Westlakes Drive for seven years. The 60,696 square-foot class A office building is located in the Westlakes Office Park in Berwyn, Pennsylvania and is 87.3 percent leased.

        Additionally, during the quarter and more recently, the Company executed leases totaling 38,247 square feet with several smaller-space users at Harborside Plaza 5 in Jersey City, New Jersey bringing the building to 64.1 percent leased.

Information About FFO

        Funds from operations ("FFO") is defined as net income (loss) before minority interest of unitholders, computed in accordance with generally accepted accounting principles ("GAAP"), excluding gains (or losses) from extraordinary items and sales of depreciable rental property (which the Company believes includes unrealized losses on properties held for sale), plus real estate-related depreciation and amortization. The Company believes that FFO per share is helpful to investors as one of several measures of the performance of an equity REIT. The Company further believes that by excluding the effect of depreciation and gains (or losses) from sales of properties (all of which are based on historical costs which may be of limited relevance in evaluating current performance), FFO per share can facilitate comparison of operating performance between equity REITs. FFO per share should not be considered as an alternative to net income per share as an indication of the Company's performance or to cash flows as a measure of liquidity. FFO per share presented herein is not necessarily comparable to FFO per share presented by other real estate companies due to the fact that not all real estate companies use the same definition. However, the Company's FFO per share is comparable to the FFO per share of real estate companies that use the current definition of the National Association of Real Estate Investment Trusts ("NAREIT"). A reconciliation of net income per share to FFO per share is included in the financial tables on page 25.

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Key Financial Data

(a)

Includes preferred units on a converted basis into common units.

(b)

Calculated based on weighted average common shares outstanding, assuming redemption of operating partnership common units into common shares.

(c)

Calculated based on shares and units included in basic per share/unit computation, plus dilutive Common Stock Equivalents (i.e. convertible preferred units, options and warrants).

(d)

Includes preferred units on a converted basis into common units and minority interests in partially-owned properties.

(e)

Funds from Operations ("FFO") is calculated in accordance with the definition of the National Association of Real Estate Investment Trusts (NAREIT). See "Information About FFO" on page 10.

(f)

Reflects square feet leased at the Company's consolidated in-service portfolio, excluding in-service development properties in lease up (if any).

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Same Store Results and Analysis
(dollars in thousands)

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Unconsolidated Joint Ventures Summary

Breakdown of Unconsolidated Joint Ventures

(a)

Property consists of a three-story theater and retail complex.

(b)

The venture is developing a family entertainment and recreation complex with an office and hotel component to be built at the Meadowlands sports complex in East Rutherford, New Jersey ("Meadowlands Xanadu"). Meadowlands Xanadu's approximately 4.76 million-square-foot complex is expected to feature a family entertainment destination comprising three themed zones: sports/recreation, children's activities and fashion, in addition to four office buildings, aggregating approximately 1.8 million square feet, and a 520-room hotel.

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Unconsolidated Joint Venture Financial Information

        The following is a summary of the financial position of the unconsolidated joint ventures in which the Company had investment interests as of March 31, 2004 and December 31, 2003:

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        The following is a summary of the results of operations of the unconsolidated joint ventures for the period in which the Company had investment interests during the three months ended March 31, 2004 and 2003:

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Select Financial Ratios

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Debt Analysis
(as of March 31, 2004)

Debt Breakdown
(dollars in thousands)

Future Repayments
(dollars in thousands)

(a)

Actual weighted average LIBOR contract rates relating to the Company's outstanding debt as of March 31, 2004 of 1.14 percent was used in calculating revolving credit facility and other variable rate debt interest rates.

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Debt Maturities
(dollars in thousands)