Multiple regression/discriminant analyses were separately conducted to generate predictors of acute and prophylactic antimanic and depressive outcome in 101 valproate-treated bipolar rapid cyclers. Predictors of good antimanic response included decreasing or stable episode frequencies and nonpsychotic mania. Predictors of good antidepressant response included nonpsychotic mania worsening over the years of the illness and absence of borderline personality disorder comorbidity. This report confirms prior findings that indicate that valproate possesses marked acute and prophylactic antimanic and antimixed effects with only poor to moderate antidepressant properties.