Tourette Syndrome is a neurological condition of unknown cause. Genetic linkage studies are aimed at finding a localization of the GTS gene on one of the human chromosomes. The genetic research of the different groups collaborating in the GTS Mapping Consortium is concentrating on systematic screening of the human genome for evidence of genetic linkage between the gene for Tourette Syndrome and DNA markers. Results of the different groups are reported regularly at workshops organized by the Tourette Syndrome Association. We were the host of the Ninth Genetic Workshop that was held in Rotterdam in June, 1993. In Rotterdam, we will concentrate our genetic linkage studies on one large Dutch TS family. If we find a positive result in this family, we will then test the other 11 Dutch families as well as the families that are being analyzed by the other members of the Collaboration. From our studies we have already eliminated a large part of the human genome. At the same time we will use slightly different alternative methods to reach the same goal. In addition to studying one large family for linkage, we will set up a study of affected brothers, sisters or brother and sister. We need a large number of sibpairs, and are still collecting blood from sibpairs. An alternative is to study affected cousins. By these additional methods we are approaching the problem of finding a chromosomal localization from different angles. Our goal is to find a chromosomal localization that can be used as a starting point in the search for the gene that is responsible for Tourette Syndrome. B. A. Oostra, Ph.D. Erasmus University, Rotterdam, The Netherlands Award $45,000 Tourette Association of America Inc. – Research Grant Award 1993