Background. Coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB) has the risk of renal dysfunction. The cause of renal dysfunction after CPB is multifactorial, such as nonpulsatile flow, renal hypoperfusion, hypothermia, and duration of CPB. This study compared off-pump technique with on-pump technique on renal function in patients who underwent CABG. Methods. Sixty patients with normal preoperative renal functions undergoing CABG were randomly assigned to conventional revascularization with CPB (on-pump) or beating heart revascularization (off-pump). Renal functions were assessed up to 10 days postoperatively. Results. Creatinine clearance was found to be significantly higher in the off-pump group than in the on-pump group (p<.05). The off-pump group had significantly less increase in creatinine levels when compared with the on-pump group (p<.05). The free water clearance values decreased similarly in both groups; however, the recovery was more prompt in the off-pump group (p<.05). No significant differences were found in the prevalence of postoperative hemodialysis. Conclusion. The off-pump technique may provide a positive contribution and sufficient protection on postoperative renal functions in patients undergoing CABG. Copyright © 2005 Taylor & Francis Inc.