A double-blind controlled study of therapeutic effects of pimozide were made in comparison with those of chlorpromazine.Subjects were 92 hospitalized schizophrenics, setting up in 46 pairs of the same sex, similar clinical conditions and with less than ten years disparity in age.One patient receiving chlorpromazine was dropped out after 4 weeks.After a one-week wash-out period, patients were first given daily 3 tablets (1 mg/tab.) of pimozide in a single dose or 6 tablets (25 mg/tab.) of chlorpromazine in three divided doses. The dose was then individualized depending on the symptoms in ratio of 1 tablet pimozide and 2 tablets chlorpromazine, within thelimits of 12 tablets or 24 tablets a day respectively.Global Comparative Judgement after 4 and 8 weeks' administration revealed no statistically significant difference between two drug groups in the sequential analysis. In General Improvement Rating after 8 weeks' administration, pimo zide caused improvement slightly better than chlorpromazine . Pimozide showed higher improvement rate than chlorpromazine after 8 weeks in items of “hal lucination”, “contact”, “working ability” and “care of clothing”.Incidence of side effects revealed no statistically significant difference between two except for salivation. Laboratory tests were also performed in all the subjects.