Twenty-four patients with left main coronary artery stenosis exceeding 50% underwent coronary artery bypass grafting from January 1991 through June 1993. Four patients [17%] had stenosis only in left main coronary artery and 20 patients [83%] had associate lesion[s] in left anterior descending , circumflex, or right coronary artery. Sixteen patients [67%] had higher degrees of stenosis [>70%] in left main coronary artery. Preoperatively 18 patients [75%] had unstable angina pectoris even during aggressive medical treatment. Preoperatively aggressive medical treatment was performed to relieve the symptom in patients with unstable angina. All patients were perioperatively treated with continuous infusion of isosorbide dinitrate to stabilize symptomatic and hemodynamic states. Twenty patients underwent elective coronary bypass surgery and 4 patients urgent operations due to severe unstable angina. There was no thirty-day mortality or late death. Angina recurred in 1 patient, but coronary angiographic study showed good patency of grafts and the symptom was relieved with medical treatment. We concluded that coronary artery bypass grafting can be safely performed by perioperative efforts, including continuous infusion of isosorbide dinitrate, for hemodynamic stabilization in patients with left main coronary artery stenosis.