Presented in part at the 151st annual meeting of the American Psychiatric Association, Toronto, May 30–June 4, 1998; the meeting of the Collegium Internationale Neuro-Psychopharmacologicum, Glasgow, July 13–16, 1998; and the meeting of the American College of Neuropsychopharmacology, Kamuela, Hawaii, Dec. 8–12, 1997. Received March 25, 1999; revisions received Aug. 5 and Sept. 24, 1999; accepted Nov. 5, 1999. From the Psychopharmacology Research Program, Department of Psychiatry, University of California, San Diego; the Psychiatric Service, San Diego Veterans Health System; the Anxiety Disorders Program, Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston; and Pfizer, Inc., New York. Address reprint requests to Dr. Rapaport, Psychopharmacology Research Program, UC San Diego, Department of Psychiatry, 8950 Villa La Jolla Dr., Number 2243, La Jolla, CA 92037; firstname.lastname@example.org. Supported by Pfizer, Inc.