Thirty-five adult chronic schizophrenic patients who had had severe persistent tardive dyskinesia for many years and who had received long-term neuroleptic therapy were treated with small repeated doses of L-dopa. After 4 weeks of treatment the intensity and frequency of involuntary movements decreased, and after 3 months orofacial and choreoathetotic dyskinetic movements diminished very much in all patients. Discontinuation of L-dopa therapy in 10 patients resulted in the return of involuntary movements after 6 weeks. Readministration of the same dose of L-dopa produced the previous therapeutic effects in all patients. Using the NIMH Abnormal Involuntary Movement Scale, the patients were rated severe (4) before treatment and mild (2) after treatment. Maintenance of all 35 patients on daily haloperidol 15 mg, or its neuroleptic equivalent, and small repeated doses of L-dopa induced a stable remission of all involuntary dyskinetic movements for the study year. The placebo control group remained unchanged with the same severe persistent dyskinetic manifestations.