Objective:This study compared the efficacy of risperidone monotherapy with risperidone plus valproate in bipolar I disorder, manic phase. Some studies showed the efficacy of risperidone monotherapy in the treatment of bipolar disorder, so we examined this effectiveness in this clinical-trial study.Method:This 7-week, randomized, single-blind study included 48 bipolar I inpatients manic phase without psychotic features divided in risperidone group (n = 23) and risperidone plus sodium valproate group (n = 25). According to clinical symptoms, 3 categories: complete remission, partial remission and no remission were mentioned in weekly follow-up. Remission rate compared with survival analysis.Results:The results showed a significant difference in remission rate between risperidone monotherapy and risperidone plus sodium valproate at the 1st, 2nd and the 3rd week (p = 0.012, 0.023, 0.027 respectively), It means the remission rate in risperidone plus valproate group was higher in the first three weeks, but at the end of the seventh week, the difference was not statistically significant. There was no significant difference between the two groups in the development of adverse effects.Conclusions:Risperidone can be effective and well tolerated in both acute manic episodes of bipolar mood disorders.