Background: Our aim was to determine whether general left main coronary artery stenosis (LMS) and ostial LMS pose additional risks after off-pump coronary artery bypass grafting (CABG) relative to non-left main coronary artery stenosis. Methods: From January 1, 2008, to December 31, 2009, 4366 patients underwent primary isolated off-pump CABG at Beijing Anzhen Hospital. Disease was retrospectively classified as non-left main disease (n = 3523), nonostial LMS (n = 765), and ostial LMS (n = 78). Groups were propensity score matched. Kaplan-Meier freedoms from major adverse cardiac and cerebrovascular events (MACCEs) were calculated. Results: During the first 30 postoperative days, mortality was significantly higher in the ostial LMS group (6.41%) than in non-left main disease (0.855%, chi(2) = 7.78, P = .005) and nonostial LMS (1.28%, chi(2) = 4.71, P = .03) groups. Incidence of MACCEs was significantly higher in the ostial LMS group (20.5%) than in non-left main disease (5.98%, P = .000) and nonostial LMS (9.62%, P = .002) groups. Odds ratio for early MACCEs of ostial LMS versus non-left main disease was 3.74 (95% confidence interval, 1.72-8.17). At mean follow-up 12.8 +/- 7.5 months and cumulative follow-up 498.5 patient-years, difference among groups in freedom from MACCEs did not reach statistical significance (chi(2) = 2.39, P = .303). Conclusions: Ostial LMS poses additional early risks of mortality and MACCEs in off-pump CABG. Off-pump CABG for ostial LMS should proceed with greater of intraoperative surveillance and lower threshold for converting to on-pump CABG. (J Thorac Cardiovasc Surg 2012;143:103-10)