Cornerstone Properties Divests Two California Properties.

Business Editors

NEW YORK--(BUSINESS WIRE)--Dec. 21, 1999

Cornerstone Properties (NYSE: CPP)

1999 Dispositions Grossed Over $495 Million

Cornerstone Properties Inc. (NYSE: CPP) announced today that it has sold two non-core buildings in two separate transactions totaling $38.75 million. The First American Title building in San Jose, California was sold to a pension fund advisor and 1300 El Camino Real, San Mateo, California was sold to an individual investor. The total square footage of both buildings was approximately 167,000 square feet and both were acquired as part of the William Wilson & Associates merger.

R. Matthew Moran, Chief Investment Officer of Cornerstone Properties, commented, "These sales conclude our disposition program for 1999 that involved 13 properties which yielded gross proceeds of over $495,000,000. The divested properties were either smaller assets or properties located in non-core markets where we felt it would be difficult to fully develop our management model."

Cornerstone Properties is a fully-integrated real estate investment trust (REIT) with a full range of development, acquisition, management and leasing capabilities. The company currently owns 83 Class A office properties throughout the U.S. totaling nearly 17 million square feet and has an additional $884 million of projects under development. The properties are located in the major suburban markets and central business districts of Seattle, Northern and Southern California, Minneapolis, Chicago, Boston, New York, Washington, D.C. and Atlanta. For more information visit the Cornerstone Properties website at www.cstoneprop.com. To sign up for our press release e-mail list, go to www.cstoneprop.com/e-mail.

This press release contains forward-looking statements within the meaning of the Federal securities laws. Forward-looking statements are inherently subject to risks and uncertainties, many of which cannot be predicted with accuracy, that could cause the actual results, performance or achievements of Cornerstone to differ materially from those reflected in such forward-looking statements. Information contained in this press release regarding current and future market conditions is based on Cornerstone's assessment of real estate markets as of this date and is subject to the uncertainties inherent in such an assessment. In particular, but not exclusively, national and regional economic conditions, the rate of new construction, and demand and supply in a given market will affect leasing activity, projected rents and the cost of lease renewals. Please see our SEC 10-Q and 10-K filings for updates to this list of risks and uncertainties.