Appropriate manipulation of dopaminergic systems, that probably contribute to tardive dyskinesia, may bring about a reduction in its intensity. In this study various, increasing doses of L-dopa, which is converted to dopamine in the CNS, was administered over the relatively long period of time of one month, in double-blind conditions, to psychiatric patients with stabilized psychotic symptoms, with tardive dyskinesia. With the one gram daily dose group, there was a reduction of the intensity of the involuntary movements, when compared to that of the patients who received placebo.