With the support of the TSA the Dutch Tourette Family Study Research Group has been able to proceed with its contributions to the collaborative efforts of GTS Gene Mapping Consortium. During the past year the collaboration within this Consortium has been further intensified, much inspired by the discussions with and the suggestions of the genetic scientists from the Scientific Advisory Board of the TSA. In collaboration with David Pauls from the Child Study Center at the Yale University School of Medicine segregation analyses have been carried out on the collaborative family data. The first combined results turned out to be consistently in agreement with the results reported in the earlier studies of the Yale group. More refined diagnostic models will be tested in the coming months. Working with Andrew Pakstis from K. Kidd’s lab at Yale, Peter Heutink summarized and published the linkage date on the polymorphic DNA markers into a comprehensive exclusion map for TS. These collaborative data have been presented in scientific publications and at scientific meetings over the past year. In addition, Peter Heutink went to the USA for several weeks to work with James Weber and Patricia Wilkie in the Marshfield Foundation, WI. Heutink focused on their microsatellite DNA polymorphisms which have proved so successful in linkage studies on other diseases. The results of their work are currently being analysed. Now that a considerable part of the genome has been excluded as possible sites for the GTS susceptibility gene(s), the development of further refined strategies with respect to identifying cases in families, statistical analyses and molecular biologic techniques in the quest for the GTS gene(s) needs increasing attention. In cooperation with the genetic statistician, Lodewijk Sandkuijl M.D., simulation studies are currently being performed using new statistical approaches to obtain more insight into the complex genetic models relevant to the heredity of GTS. The strong sense of collaboration within the Consortium will be fundamental for the continuation of these developments. Ben J.M. van de Wetering, M.D., Peter Heutink, Ben A. Oostra, Ph.D., Martinus F. Niermijer, M.D., Ph.D. Erasmus University, Rotterdam, The Netherlands Award $50,000 Tourette Association of America Inc. – Research Grant Award 1991