Purpose: This study evaluated the early and midterm results of offpump coronary artery bypass (OPCAB) for left main coronary artery (LMCA) stenosis. Methods: Patients treated between November 2001 and December 2006, during which isolated coronary artery bypass grafting (CABG) was performed without cardiopulmonary bypass in principle, were included. Isolated CABG was performed in 206 patients, of whom 62 (30.1%) had LMCA stenosis > 50%. Results: The in-hospital mortality rate (LMCA stenosis > 50%, 1.6%; LMCA stenosis <= 50%, 0.7%, p = 0.512), the incidence of postoperative complications, and the midterm survival rate (LMCA stenosiss50%, 86.7 +/- 5.2%/5 years, LMCA stenosis <= 50%, 89.6 +/- 3.8%/5 years, p = 0.21) did not significantly differ between the two groups. Conversion was significantly frequent in patients with LMCA stenosis > 75% and severe stenosis > 90% in the right coronary artery (RCA) trunk. Conclusions: Patients with LMCA stenosis can undergo OPCAB safely and the midterm results are good. As conversion was significantly frequent in patients with severe LMCA and RCA trunk stenosis, adequate preparation for pump application is necessary. (J Card Surg 2009;24:162-166).