A prospective study was performed to monitor the postoperative changes in biochemical markers associated with reperfusion injury following (i) cardiopulmonary bypass (CPB) with aortic cross-clamping and cardioplagia (CABG); (ii) CPB with a tissue stabilizing device (SUP.CPB); or (iii) surgery on beating heart (off-pump CABG or OPCABG). Of the 48 patients, 16 were subjected to CABG, 16 to SUP.CPB, and 16 to OPCABG. Arterial and venous blood samples drawn 10 min preoperatively and 0.2, 4, 24, and 48 hr after surgery were assayed for plasma lactate, total calcium, and ionized calcium and erythrocyte glutathione peroxidase (GPX) and superoxide dismutase (SOD). Results revealed that ionized calcium, SOD, and GPX levels of all patients increased at 4 hr following surgery but returned to baseline levels at 24 or 48 hr after surgery. Increased postoperative GPX levels reflect a cellular defense mechanism against oxidative damage during reperfusion, while lactate levels during reperfusion reflect delayed recovery of aerobic myocardial metabolism. The postoperative release of lactate, GPX, and SOD in patients undergoing the CABG (on-pump) technique was significantly higher compared to those subjected to OPCABG or SUP.CPB. There were no significant differences in postoperative patterns of release of biomarkers in patients with OPCABG vs SUP.CPB, suggesting that these surgical techniques are equally acceptable.