Background: This prospective non-randomized clinical study was done to compare Off-pump and On pump myocardial revascularization by Troponin I release in patients undergoing first elective coronary artery bypass graft used to evaluate myocardial injury. Methods: One hundred an twenty patients were non-randomly assigned to a Off-pump or On-pump myocardial revascularization group. Cardiac Troponin I (CTnI) were measured in serial venous blood samples drawn preoperatively in both groups. In On-pump group after aortic unclamping at 12 and 24 hours and in Off-pump group after the last distal anastomosis at 12 and 24 hours.