Received June 30, 1997; revision received Nov. 24, 1997; accepted Dec. 22, 1997. From the Departments of Psychiatry and Diagnostic Radiology, and VA Medical Center, Yale University School of Medicine, New Haven, Conn.; the Department of Psychiatry, Emory University School of Medicine, Atlanta; the Butler Hospital, Department of Psychiatry and Human Behavior, Brown University School of Medicine, Providence, R.I.; and the Dallas VA Medical Center. Address reprint requests to Dr. Malison, Clinical Neuroscience Research Unit, Abraham Ribicoff Research Facilities, Connecticut Mental Health Center, 34 Park St., New Haven, CT 06519; firstname.lastname@example.org (e-mail). Supported by National Institute on Drug Abuse grants DA-09330 (Dr. Price), DA-04060, DA-09250, DA-0112 (Dr. Kosten), DA-00167 (Dr. Malison), DA-00216 (Dr. McCance), and DA-09294 (Dr. Innis); NIH grant RR-00125 from the General Medical Clinical Research Center; the State of Connecticut Department of Mental Health and Addiction Services; the Stanley Foundation (Dr. Price); and the National Alliance for Research on Schizophrenia and Depression (Dr. Malison). The authors thank E.O. Smith, G. Wisniewski, S. Zoghbi, M.D. Stratton, Y. Zea-Ponce, M.K. Madrak, L. Pantages-Torok, and R. Weiss for their assistance and John Neumeyer, Ph.D., for supplying the tributylstannyl precursor used in the preparation of [123I]β-CIT.