The occlusive coronary artery disease presents a potential threat to a significant population in the United State. According to many case reports, the increasing incidence of coronary artery disease due to atherosclerosis is noted in Korean, recently. We experienced one case of coronary artery disease. He was a 68 year old male who had been suffered from hypertension since 1 5 years ago, and had intermittent conservative treatment at local clinic. He had been afflicted with severe chest pain on exertion, but this symptom was relieved on rest. Pre-operative EKG finding revealed no any other ischemic sign. Significant S-T segment depression was noted at lead II, aVF, V3, V4, and V5, and inverted T wave in V5 and V6 after Master`s test. Simple chest X-ray finding showed emphysematous field, bilaterally. Final pre-operative diagnosis was made by coronary angiogram, which showed almost 90% degree of occlusive lesion in the proximal part of left main coronary artery above the origin LAD artery. He was treated successfully by aorta-coronary saphenous vein graft under extra-corporeal circulation in May, 1987. He has been followed up with uneventful course.