Presented in part at the Congress of the International Association for Child and Adolescent Psychiatry and Allied Professions, Stockholm, August 2–7, 1998. Received Nov. 23, 1998; revisions received Dec. 15, 1999, and June 1, 2000; accepted July 5, 2000. From the Departments of Psychiatry and Pediatrics, Medical School, University of São Paulo, São Paulo, Brazil; and the Child Study Center, School of Medicine, Yale University. Address reprint requests to Dr. Mercadante, Child Study Center, Yale University, 230 South Frontage Rd., P.O. Box 207900, New Haven, CT 06520-7900; firstname.lastname@example.org (e-mail). Supported in part by grants from the Fundação de Amparo à Pesquisa do Estado de São Paulo (5012-7, 5013-3, 11991-0, and 7525-0) and the Conselho Nacional de Desenvolvimento Científico e Tecnológico (521369) to Drs. Miguel and Mercadante and from NIMH (MH-01527 and MH-49351) to Drs. Lombroso and Leckman. The authors thank Drs. José Alberto del Porto, Orlando Barreto, Vanda Bastos, Eunice Mitiko Ocuda, and Silvana Brasilia Sachetti for reviewing this manuscript.