Between April, 1984 and December, 1988, 450 adult patients underwent open heart surgery for the valvular heart disease (VHD) and ischemic heart disease (IHD) in our institution. As the postoperative complication, LOS was observed in 33 patients with VHD (14.2%), and in 27 patients with IHD (12.4%) with no significant difference between the two groups. Treatment for LOS employed in this series consisted of pharmacological therapy in 11 patients, IABP in 42, IABP+veno-arterial bypass (VAB) in 5, right heart bypass (RHB)+IABP in 1 and left ventricular assist device (LVAD)+IABP in 1. All patients who were treated by the pharmacological therapy were alive and were discharged. Eighty-one % of the patients who were assisted with IABP were able to weaned off IABP, and 57% of the patients were alive and were discharged. All patients who were assisted with IABP+VAB died of LOS within 3 days after the operation. One patients who was assisted with RHB+IABP for pulmonary hypertension after emergency re-MVR and the other patient with LVAD+IABP for LOS after emergency CABG were able to be weaned off the assisted circulation and were discharged from the hospital. The salvage rate of patients with IHD by mechanical assisted circulation was generally higher than that of patients with VHD. Because of the limitation of IABP or VAB effect on the hemodynamic, LVAD directly assisted cardiac function would be indicated for severe LOS following open heart surgery without delay.