Often, the efficacy and tolerability of standard medications prescribed for Tourette Syndrome (TS) and co-occurring disorders (e.g. OCD and ADHD), is limited. At the same time, we are seeing increased use of complementary and alternative treatments among the community. Some children with TS have been anecdotally described as deriving benefit from fish oil. However, no scientific studies on the efficacy of this substance have ever been done. The purpose of this study is to test the efficacy and safety of omega 3 fatty acids derived from fish oil in the treatment of children and adolescents with TS. We hypothesize that orally administered Omega 3 fatty acids will reduce tics and obsessive compulsive symptoms in children and adolescents with TS through pro-serotonergic and antiinflammatory effects. In both TS and OCD there is considerable evidence suggesting the involvement of serotonin dysfunction and in a subgroup of children, an autoimmune process may be involved as well. There are also scientific data suggesting that serotonin dysfunction is triggered by inflammatory mediators such as cytokines. Omega 3 fatty acids appear to act by down-regulation of pro-inflammatory cytokine production and through pro-serotonergic activity, thus addressing some of the pathways implicated in the pathogenesis of TS and OCD. Fish oil has also received attention as a therapeutic agent in autoimmune illnesses. In this 20 week, double blind, placebo controlled, parallel group study using a flexible dose titration design, 40 patients, ages 6-18, will be randomly assigned to receive either omega 3 fatty acids or placebo. Omega 3 fatty acids will be initiated at a dose of 500 mg. and flexibly titrated to a possible maximum dose of 6000mg. Clinical ratings, completed at baseline and weeks 1,2,3,4,6,8,12,16 and 20 after the initiation of the study, will include the Yale Global Tic Severity Scale, Yale-Brown Obsessive Compulsive Scale and Clinical Global Impressions Scale for Tics and OCD. We hypothesize that omega 3 fatty acids will be significantly more effective than placebo in reducing TS and OCD symptoms. If this hypothesis is confirmed, these results will provide support for future studies of complementary and alternative agents. Vilma Gabbay, M.D. and Barbara J. Coffey, M.D., M.S., New York University Child Study Center, New York, NY Award: $75,000 This study is underwritten through the generosity of pauline Whitaker and Ginger and Don Whitaker Tourette Association of America Inc. – Research Grant Award 2003-2004