Aim. Myocardial ischemia/reperfusion injury in patients undergoing coronary artery by-pass grafting (CABG) involves the reperfusion-induced conversion of reversible injured myocardial and endothelial cells. N-acetylcysteine (NAC) has a potential being the minimization of the impact of reperfusion injury. The aim of this study was to evaluate the effects of intravenous NAC on peri-procedural myocardial injury after CABG.