GTC BIOTHERAPEUTICS TO HOST FIRST QUARTER 2009 EARNINGS CALL AND WEBCAST ON WEDNESDAY, MAY 13, 2009

Framingham, Mass., May 7, 2009-- GTC Biotherapeutics, Inc. (Nasdaq: GTCB) (“GTC”) announced today that its financial results for the first quarter 2009 will be released on Wednesday, May 13, 2009 followed by a webcast conference call starting at 10:00 a.m. Eastern Time. You may access the live internet broadcast or the subsequent archived recording, on GTC’s website at http://www.gtc-bio.com or access the conference call as follows:

Live Call – In the United States, dial 1-888-713-4214
Outside the United States, dial 617-213-4866
Reference call ID: when prompted 98323028

Audio Archive – In the United States, dial 1-888-286-8010
Outside the United States, dial 617-801-6888
Reference call ID: when prompted 24201578

Participants may pre-register for the call at: https://www.theconferencingservice.com/prereg/key.process?key=PAFRFKG8V Pre-registrants will be issued a pin number to use when dialing into the live call which will provide quick access to the conference by bypassing the operator upon connection.

NOTE: a replay of the call will be available one hour following the end of the call and will be accessible until May 20, 2009.

The earnings webcast is also being distributed over CCBN's Investor Distribution Network to both institutional and individual investors. Individual investors can listen to the call through CCBN's individual investor center at www.earnings.com or by visiting any of the investor sites in CCBN's Individual Investor Network. Institutional investors can access the call via CCBN's password-protected event management site, StreetEvents (www.streetevents.com).

About GTC Biotherapeutics

GTC Biotherapeutics develops, supplies, and commercializes therapeutic proteins produced through transgenic animal technology. ATryn®, GTC’s recombinant human antithrombin, has been approved for use in the United States and Europe. ATryn is the first and only transgenically produced product to be approved for therapeutic use anywhere in the world. In addition to ATryn, GTC is developing a portfolio of recombinant human plasma proteins with known therapeutic properties. These proteins include recombinant forms of human coagulation factors VIIa, VIII, and IX, which are being developed for the treatment of hemophilia, and alpha-1 antitrypsin. GTC is developing a monoclonal antibody to CD20 with enhanced ADCC (antibody-dependent cell-mediated cytotoxicity), and a proprietary monoclonal antibody to CD137 with potential indications in oncology and autoimmune disease. GTC is also developing a portfolio of follow-on biologic monoclonal antibodies. GTC’s intellectual property includes a patent in the United States through 2021 for the production of any therapeutic protein in the milk of any transgenic mammal. GTC’s transgenic production platform is particularly well suited to enabling cost effective development of proteins that are difficult to express in traditional recombinant production systems as well as proteins that are required in large volumes. Additional information is available on the GTC web site, http://www.gtc-bio.com.

CONTACT:
GTC Biotherapeutics, Inc.
Thomas E. Newberry
Vice President, Corporate Communications and Government Relations
(508) 370-5374 or tom.newberry@gtc-bio.com