Presently marketed antiparkinsonism drugs are potent anticholinergic agents that, while effective in treating extrapyramidal symptoms (EPS), also are productive of or can exacerbate a number of side effects associated with psychotropic drugs. Some of these include gastrointestinal disturbances, visual difficulties, and tardive dyskinesia. A double-blind study was carried out to assess the efficacy (and adverse effects) of amantadine hydrochloride--an agent without appreciable anticholinergic activity--for the treatment of drug-induced EPS. Amantadine was found to be comparable in effect to benztropine mesylate, but with fewer side effects. The potential role of amantadine may be in the treatment of patients with drug-induced EPS for whom medication with anticholinergic properties is contraindicated.