A case of acute myocardial infarction due to the lesion in the left main coronary artery was reported. A 50-year male was referred to our department for suspected acute myocardial infarction. Physical examination on admission revealed slight cyanosis with cold sweating due to severe chest pain. Pulse was irregular and heart rate was 78 beats/min. Blood pressure was 100/80 mmHg. A series of electrocardiograms (ECG) and laboratory data provided the diagnosis of wide-ranged anterolateral infarction in the left ventricle. Emergency coronary angiograms taken without delay showed a subtotal occlusion (99% stenosis) of the left main coronary trunk (LMT) before the initiation of intracoronary thrombolysis (PTCR). Following the intracoronary infusion of urokinase of 1,200,000 units, symptoms and ECG changes transiently improved but worsened later, and LMT stenotic lesion and delayed filling of myocardium were similar with before PTCR. Emergency coronary-aorto bypass graft (CABG) was undertaken without a significant delay to both the left anterior descending artery (LAD) and left circumflex coronary artery (LCX). With these treatments, the patient could survive despite the wide area of infarction due to LMT lesion. Coronary angiograms performed 37 days after the CABG showed that the graft to LAD was completely occluded and the LCX graft was patent with partial stenosis. Treadmill test at this time induced an anginal episode with ischemic ECG changes on moderate exercise, indicating the presence of significant area of ischemic myocardium. For salvage of the ischemic myocardium, percutaneous transluminal coronary angioplasty (PTCA) was successfully performed for the LMT stenosis, resulting in no episode of angina nor ischemic ECG changes during exercise loading.(ABSTRACT TRUNCATED AT 250 WORDS)