It is well known that the use of cardiopulmonary bypass (CPB) influences renal function and occasionally results in renal failure following cardiac surgery. Coronary artery bypass grafting (CABG) without CPB may avoid this and preserve the perioperative renal function. The present study enrolled 52 patients undergoing CABG without CPB (OPCAB group) and matched them for renal function and prognostic variables with 53 patients undergoing conventional CABG (CABG group). Perioperative renal function and early clinical results were assessed. The OPCAB group had significantly less increase in creatinine levels (0.16 +/- 0.05 vs 0.45 +/- 0.06 mg/dl; p = 0.01) and greater creatinine clearance (81.6 +/- 7.3 vs 56.3 +/- 4.8ml/min; p = 0.01) postoperatively. Postoperative recovery of free water clearance was more prompt in the OPCAB group. The duration of intubation and intensive care unit stay was significantly shorter, and the creatine kinase-MB release and blood transfusion requirements were significantly less in the OPCAB group. The OPCAB technique preserved glomerular filtration rate and prevented the increase in creatinine levels. The results suggest that the technique enables earlier patient recovery and gives superior renal protection compared with conventional CABG.