Nine centers in five countries are cooperating in a TSA-sponsored collaborative research effort to identify the gene(s) that cause TS. This genetic consortium is continuing its clinical assessment and DNA analyses of 100 pairs of clearly affected siblings with TS. Moreover, the collaborators have begun collection of preliminary information for the second phase to include an additional 100 sibpairs. The clinical data and DNA materials are centralized in two locations, and the statistical analyses are being coordinated by the Project Director, Professor Lodewijk Sandkuijl of Leiden University, The Netherlands. PARTICIPATING CENTERS Canada Toronto Western Hospital, Toronto, Ontario Germany Klinikum der Philipps-Universitat, Marburg The Netherlands University Hospital Rotterdam-Dijkzigt, Rotterdam United Kingdom University College, London Medical School, London United States Yale University/Child Study Center, New Haven, CT Marshfield Medical Research Foundation, Marshfield, WI Strong Memorial Hospital, University of Rochester, Rochester, NY Johns Hopkins Medical Institutions, Baltimore, MD Primary Children’s Hospital, Salt Lake City, UT Award – $100,000 (Clinical Assessment of 100 Sibpairs) $80,000 (Laboratory DNA Analyses) Tourette Association of America Inc. – Research Grant Award 1996