Objects : Manic phase of bipolar disorder is treated with a combination of mood stabilizer and antipsychotic drug, especially in the acute phase. Such combined treatment is often required for the clinical management of manic symptoms until therapeutic effects of mood stabilizer become evident. The present study was the first open trial to evaluate the efficacy of risperidone, and safety of the combination of mood stabilizer and risperidone in the treatment of acute manic patients. Method : This study was performed as an open clinical study. The subjects of this study were 42 patients who had been admitted with first manifestations or acute exacerbations of illness were selected, using DSM-III-R criteria for bipolar disorder, manic episode. Patients were rated using the the Brief Psychiatric Rating Scale (BPRS), Clinical Global Impression (CGI), Extrapyramidal Symptom Rating Scale(ESRS). Other adverse events were assessed by a symptom checklist and by observation by medical personnel. Vital signs were monitored in a standard way and electrocardiography, routine laboratory analysis were performed. Results : Thirty patients(67%) completed the 12-week trial period. The CGI showed a good therapeutic effect with a minimal incidence or severity of side effects. The majority of patients showed a continuos reduction in their BPRS scores. The extrapyramidal symptoms assessed on ESRS generally showed mild to moderate degree. laboratory porameters showed no significant changes during the course of treatment. Conclusion : The results of the study showed a good efficacy of the risperidone in manic patients and further controlled studies are warranted.