The authors conducted a double-blind, controlled study to test the behavioral, affective, and neurological effects of antiparkinson drug discontinuation. Patients were evaluated at baseline and at 2 and 4 weeks. Of 24 placebo patients 9 left the study early because of adverse effects; none of the 8 patients in the antiparkinsonian group did so. The placebo group had significantly more lower extremity movements, motor agitation, hallucinations, and physical complaints at 2 weeks and scored significantly higher in depression at 4 weeks. A sizable proportion of chronic, drug-treated schizophrenic patients appear to need antiparkinsonians for clinical stability.