Received March 28, 2003; revision received Sept. 9, 2003; accepted Sept. 29, 2003. From the Department of Psychiatry, Harvard Medical School, Boston; the Department of Epidemiology, Harvard School of Public Health, Boston; the Harvard Institute of Psychiatric Epidemiology and Genetics, Boston; the Department of Psychiatry, the Johnson and Johnson Center for Pediatric Psychopathology, and the Stanley Center for Pediatric Mania, Massachusetts General Hospital; and the Massachusetts Mental Health Center, Boston. Address reprint requests to Dr. Faraone, Pediatric Psychopharmacology Research, WRN 705, Massachusetts General Hospital, 55 Fruit St., Boston, MA 02114-3139; firstname.lastname@example.org (e-mail). The linkage analysis and manuscript preparation were supported in part by NIMH grants MH-57934 and MH-59126 and by grant HD-37694 from the National Institute of Child Health and Human Development (Dr. Faraone, principal investigator), by NIMH grants MH-43518, MH-59624, and MH-60485 (Dr. Tsuang, principal investigator), and by grants from the Stanley Foundation (J. Biederman, principal investigator) and Johnson and Johnson (J. Biederman, principal investigator). This work was completed when Dr. Glatt was a trainee in the NIMH-funded Psychiatric Genetics Training Program at the Harvard Institute of Psychiatric Epidemiology and Genetics (MH-60485, Dr. Tsuang, principal investigator). The clinical data and genotypes were provided by the NIMH Human Genetics Initiative data repository. The clinical data were collected at four sites: Indiana University, Johns Hopkins University, NIMH Intramural Research Program, and Washington University. The principal investigators at these sites were J. Nurnberger, J. DePaulo, E. Gershon, and T. Reich, respectively. The lead NIMH investigator was M. Blehar. The genotypes were generated in the laboratories of A. Goate, Ph.D., Department of Psychiatry, Washington University School of Medicine; H. Edenberg, Ph.D., Indiana University School of Medicine, S. Detera-Wadleigh, NIMH Intramural Research Program, and O. Stine, Johns Hopkins University School of Medicine.