1. Obsessive Compulsive Behaviours (OCB) occur in more than 50% of patients with the Gilles de la Tourette Syndrome (GTS) and in some cases these behaviours are more disabling than the tics themselves. 2. Fluoxetine, a specific serotonin reuptake inhibitor (SSRI) has been demonstrated to be effective in patients with Obsessive Compulsive Disorder. 3. The authors report on their clinical experience of fluoxetine in 30 GTS patients with OCB, in an open retrospective study. 4. There was an overall improvement in OCB as judged by the clinician in 76% of cases. Most patients received fluoxetine at a daily dose of 20 to 40mg for an average period of 6 months (24 +/- 4 weeks). In general, fluoxetine was well tolerated and further studies are indicated.