The purpose of this study was to investigate the efficacy of risperidon. The authors examined 35 schizophrenic patients. After 6 months clinical improvement was shown in 22 patients (63% of the examined patients), and after 12 months clinical improvement was shown in 15 patients (43% of the examined patients). Risperidon was the drug of choice for 9 patients (60% of patients with improvement). The incidence of extrapyramidal side effects was slight and dose-related.