A 68-year-old woman with recurrent chest pain was referred to our institution. Coronary angiography showed 100% obstruction of the left main trunk, the proximal right coronary artery with good collaterals to the left anterior descending artery and left circumflex artery along the conus artery. Emergency surgical revascularization was undertaken with two saphenous vein grafts. The saphenous vein grafts were placed in the left anterior descending artery, obtuse marginal branch and the posterolateral and posterior descending coronary arteries with excellent flow. The postoperative course was uneventful and follow-up angiography was obtained 20 days after the surgery. Coronary angiography demonstrated a saccular aneurysm (10 x 9 mm) originating at the distal segment of the left main coronary artery with 90% stenosis, and excellent patency of both saphenous vein grafts. Follow-up angiography was performed 1 and 3 years after the surgery. The size of the left main coronary aneurysm remained unchanged at both examinations. The patient did well with no further cardiac symptoms after 5 years.