The three hundred and sixty nine patients who underwent either isolated or concomitant coronary artery bypass graft surgery since May, 1977 till December, 1993 at the Yonsei University Cardiovascular center were studied with respects to the incidence of operative risk factors, surgical methodology and consequent results. The patients were classified into two periods, according to the time of the surgery in relation to the date of the opening of the Yonsei cardiovascular center. Period I[1977 to 1990 , consisting of the patients who underwent surgery prior to the opening date, harboured a total of 189 patients with the mean age of 55 years, and the second, Period II[1991 to 1993 , those who underwent after the opening, of 180 patients with the mean age of 60 years. The Period II patients were involved in more operative risk factors, compared to the ones in Period I. The anatomy of the coronary arteries of the patients of Period II were more likely to have multilesional and left main disease. The patients in Period I were older, had more prominent left ventricular dysfunction and were more likely to be exposed to the risk factors. The number of implanted grafts were greater period II[average of 2.5 grafts per patient in Period I VS 3.2 in Period II and the frequency which the used left internal mammary artery was also significantly higher in Period II[49 and 104 cases in Period I and Period II . The incidence of perioperative myocardial infarction was 20 patients[10.6% in Period I, 14 patients[7.8% in period II. And the operative mortality was 20 patients[10.6% in period I, 8 patients[4.4% in period II. In conclusion we think that the operative results have improved in Period II, compared to that of Period I, in spite of the higher risks, due to accumulation of surgical experiences, improved surgical techniques and myocardial protection, specialized teamwork, application of the intraoperative TEE and appropriate pharmacological interventions by anesthesiologist.