Three patients suffering from Gilles de la Tourette Syndrome were initially treated with haloperidol. Depressive side effects and symptom breakthrough necessitated the search for another agent. The efficacy of lithium carbonate in treating stereotyped hyperkinetic behavior (such as is seen in Gilles de la Tourette syndrome) prompted the evaluation of lithium carbonate. An objective behavioral observation technique, clinical ratings and the patient's subjective reports were used to systematically record the response to treatment during the entire course of the study. Initially blood plasma Li+ levels in the 0.5 to 0.6 mEq/L range were obtained and these correlated with reduced frequency, as well as intensity, of involuntary motor acts (tics) and sounds. When the Li+ blood levels had stabilized at 0.8 to 0.9 mEq/L the major tics and involuntary sounds cleared dramatically. The patients experienced no side effects and have been followed for several months without recurrence of the original symptoms.