To compare the effects of intra-aortic balloon pumping (IABP) between use for coronary artery bypass grafting (CABG) and for valve replacement, the results were reviewed in 513 patients who underwent CABG (n = 215) or valve replacement (n = 298). The rate of weaning from IABP and in-hospital survival after IABP support were excellent in CABG patients, where all 21 CABG patients (100%) and 17 out of 25 valve replacement patients (68%) could be weaned from IABP, and 19 out of 21 CABG patients (90%) and 14 out of 25 valve replacement patients (56%) survived for a long period. From comparative studies of pre- and postoperative data, the duration of IABP support in patients who could be weaned from IABP or who achieved in-hospital survival tended to be more prolonged in patients with valve replacement than in those with CABG. Among patients having IABP postoperatively, 4 CABG patients and 8 valve replacement patients had definite indications for IABP support. In the other 34 patients, preoperatively depressed cardiac function was observed in 12 patients where most of them were patients with valve replacement. Postoperative improvements in cardiac index were not as marked in patients undergoing valve replacement with IABP. The outcome for patients who had definite causes of post-operative cardiac failure, which were more numerous in the valve replacement group, was poor even if they could be weaned from much longer IABP support. In conclusion, the IABP was more effective in patients with CABG compared with those with valve replacement, because the number of patients who had a depressed cardiac function during the pre- and postoperative periods was lower in the CABG group and the incidence of serious perioperative complications was less frequent in these patients.