A 63-year-old man was admitted with severe chest pain. The electrocardiogram demonstrated ST-segment depression in the anterior and lateral leads suggesting acute anterior myocardial ischemia. Contrast-enhanced thoracic computed tomography performed due to severe back pain showed acute dissection of the descending aorta. Coronary angiography showed normal coronary arteries. Transesophageal echocardiography revealed a Stanford type A aortic dissection involving the left main coronary ostium and causing left main coronary occlusion. The dissected flap caused partial obstruction of the coronary ostium and occasional separation of the lumen, resulting in nonsustained ventricular tachycardia. At emergency operation, the entry of the dissection was seen in the ascending aorta and the dissection extended throughout almost the entire sinus of Valsalva and the left main coronary trunk. The aortic flap was seen in the coronary ostium. Both the right and left coronary arteries were prepared widely and sutured directly to a composite graft. The ascending aorta was replaced with a composite graft through a Bentall procedure. Descending aortic repair was planned for a subsequent operation. The patient was hemodynamically stable for three weeks, but then developed respiratory insufficiency due to severe nosocomial pneumonia and died one month after the operation.