Preliminary studies with PET-scanner and nuclear magnetic resonnance have shown no abnormalities in Gilles de la Tourette syndrome. Estimation of homovanillic acid, the main metabolic of dopamine, in the cerebrospinal fluid of patients with Gilles de la Tourette disease suggests that brain dopaminergic receptors are hypersensitive. Such an hypersensitivity of dopamine receptors is in agreement with the clinical improvement of patients treated with neuroleptic drugs. The study with PET-scanner presented here suggests the existence of a neuronal hypofunction in some striatal and corticolimbic area in patients.