A preliminary trial with fluoxetine, a 5-HT reuptake inhibitor, was carried out on two young male patients (21 and 32 years old) affected by Gilles de la Tourette syndrome. They both underwent a complete neurological evaluation also including neuroradiological, neurophysiological and neuropsychological assessment. Both patients had already been treated with benzodiazepines and amitriptyline; the older one was also given haloperidol and chlorimipramine with definite, but short-lasting improvement. During hospitalization a therapeutic trial with fluoxetine (20 mg/day in the younger patient and 40 mg/day in the older) in association with chlorimipramine (75 mg/day) was initiated, leading to a significant reduction (at least 50%) of abnormal movements and obsessive-compulsive behaviour. The older patient had no side effects while the 21 year old subject complained of insomnia, urinary retention and anorexia; despite the objective improvement, these side effects led us to modify the therapy after the first month. The favourable action of serotoninergic agents on TS symptoms supports the hypothesis that the multiple tics of the syndrome are motor compulsions.