This study of 34 patients with Gilles de la Tourette's syndrome describes the treatment of 21 patients who were followed for two months to five years. Thirteen patients were excluded from the overall analysis because they did not fulfill criteria for inclusion in this report. Haloperidol was a difficult drug to use effectively. The dosage varied between 6 and 180 mg and had to be titrated against an endpoint of efficacy compared with side effects. Most patients were able to achieve over 90% decrease in their symptoms after one year of treatment. Other minor and major tranquilizers were less effective. Other chemotherapy and psychotherapy were ineffective. Spontaneous decrease or increase of symptoms are common and lead to difficulty in evaluation of clinical course.