This longitudinal, blind study of Gilles de la Tourette's disease in a 44 year old male patient who was nonresponsive to Haloperidol therapy indicates that dopamine excretion is related to clinical response. An increased urinary excretion of dopamine and some of its metabolites was associated with the failure of Haloperidol therapy. Imipramine, administered to treat the patients' depressive mood that emerged in the course of treatment, decreased the urinary excretion of dopamine and moderately alleviated the symptoms of Tourette's syndrome. The results suggest that monitering urinary dopamine and 3-methoxytyramine excretion in Tourette's disease may predict the clinical response to pharmacotherapy, and that a dopaminergic mechanism may be associated with this type of motor hyperkinesia.