A Cochrane review included 6 studies with a total of 1 343 subjects. Risperidone monotherapy was more effective than placebo in reducing manic symptoms, using the Young Mania Rating Scale (YMRS) (weighted mean difference (WMD) –5.75, 95% confidence interval (CI) –7.46 to –4.04, P<0.00001; 2 trials) and in leading to response, remission and sustained remission. Effect sizes for monotherapy and adjunctive treatment comparisons were similar. Low levels of baseline depression precluded reliable assessment of efficacy for treatment of depressive symptoms. Risperidone as monotherapy and as adjunctive treatment was more acceptable than placebo, with lower incidence of failure to complete treatment (RR 0.66, 95% CI 0.52 to 0.82, P = 0.0003; 5 trials). Overall risperidone caused more weight gain, extrapyramidal disorder, sedation and increase in prolactin level than placebo. There was no evidence of a difference in efficacy between risperidone and haloperidol either as monotherapy or as adjunctive treatment.