We evaluated operative results of emergency aortocoronary bypass grafting in 17 patients (surgical group) with impending myocardial infarction or acute myocardial infarction, and compared them to those of medical therapy in 16 patients (medical group) required IABP with same condition. Mortality in surgical group is significantly lower than that in medical group. In patients with severe coronary artery disease, mortality in surgical group is significantly lower than that in medical group. In patients with severe left ventricular dysfunction, mortality in surgical group is significantly lower than that in medical group. The period using IABP before the operation in expired patients is longer than that in survived patients. These data indicate that emergency operation should be performed immediately after IABP in patients with severe coronary artery disease or severe left ventricular dysfunction.