The operative results in 32 patients who underwent aortic valve replacement with aortic occlusion and normothermic myocardium (group 1) were compared with 54 similar patients in whom the myocardium was protected by hypothermic coronary perfusion through the aortic root (group 2). The operative mortality and the incidence of heart failure, subendocardial ischemia and myocardial infarction were the same in the two groups. The maximal concentrations of cardiac enzymes after operation in group 2 patients were significantly lower than those in group 1. The postoperative cardiac performance was significantly different in that only 5.6% of group 2 patients required inotropic agents after operation compared with 25% of group 1 patients. The patients in group 2 were easier to defibrillate after cardiopulmonary bypass.