Background: In an attemp to avoid the adverse effect of the cardiopulmonary bypass, off pump CABG has recently been rediscovered and refined. We compared the hospital outcome of patients done off pump with those done on pump CABG. Method: Between January 2001 and June 2003, 424 off pump CABG and 258 on pump CABG were performed in Yonsei Cardiovascular Center excluding the patients with other procedures. Results: Off pump and on pump CABG did not show any differences in their risk factors. Off pump CABG group had significantly lower mean operation time(p<0 .0001) and mean CK-MB level(p<0.0001), and significantly shorter ICU stay(p=0.0050) and hospital stay(p<0.0001). On pump had significantly more distal grafts than off pump CABG groups(p<0.0001). Off pump CABG and on pump CABG groups did not show any differences in their postoperative complications and outcomes. But neurologic complications developed more common in on pump CABG group(p=0.0086). Conclusions: This study showed that patients having off pump CABG are not exposed to a greater risk of adverse outcomes and also provided evidence that patients having off pump CABG have significantly lower operation room time and CK-MB level and significantly shorter ICU stay and hospital stay.