Background: Emergency conversion to cardiopulmonary bypass in off-pump coronary artery bypass grafting (OPCAB) is recognized to increase operative mortality and morbidity. How ever less has been talked about the time of conversion and on pump beating heart revascularizations .Methods: In this study out of 380 planned off-pump coronary artery bypass procedures done between August 2002 to July 2006, 12 patients required emergency conversion, of which three patients were after haemodynamic collapse, and nine patients were semi elective conversions before haemodynamic collapse.Results: The operative mortality in the conversion group was 25%, as compaired to 1.4% in the non conversion group. We analyzed that the time of conversion plays an important role in the overall outcome Though the operative mortality was 25% in the conversion group the operative mortality in the semi-elective conversion group was 0%. The requirement of inotropes, requirement of intra aortic balloon support, and postoperative multi organ dysfunction was more in the delayed conversion compaired to the semi-elective conversion group. The criteria for semi-elective conversion were unexplained Hypotension requiring inotropes, raised left ventricular end diastolic pressure (LVEDP), decreased urine output (less than 1cc/ kg) unexplained tachycardia, unexplained arrhythmias and blood loss requiring more than two blood transfusions.Conclusions: We conclude that delayed conversion is associated with poor surgical outcome however semi-elective conversion before haemodynamic collapse with on pump beating heart bypass revascularisaion is a safe and viable option. (Ind J Thorac Cardiovasc Surg, 2007; 23: 184-187)