This study was designed to determine if topical cardiac hypothermia is a necessary adjunct to intraoperative myocardial protection. In this study, 105 patients ranging in age from 22 to 74 years were included. Myocardial temperature was measured at the ventricular septum. All patients received cold blood cardioplegia without topical cooling. In most of the patients(90%) the myocardial temperature was dropped to 10-15degrees C without topical cooling. In Group A, myocardial temperature was dropped rapidly to 10-15degrees C with, 1,000ml or less cardioplegic solution. In Group B, the amount of cardioplegic solution required for lowering myocardial temperature to 10-15degrees C was 1,000-2,000ml. In Group C, myocardial temperature was not dropped below 18degrees C or cardioplegic solution over 2,000ml was required for lowering myocardial temperatur. Eight patients(8/61, 8%) in group A, 12 patients(12/35, 34%) in group B and 8 patients(8/9. 89%) in group C had Complete obstructive lesions in at least one of major branches of coronary artery(p=0.001). Myocardial perfusion score was different among the groups(8.27+/-2.27 in group A, 9.98+/-2.21 in group B, 10.30+/-2.49 in group C, p<0.002). These data suggest that routine topical hypothermia may be unnecessary if myocardial temperature of less than 15degrees C could be attained with cold blood cardioplegia, especially in case of myocardial perfusion score below 10.