Renal insufficiency (RI) is a prognostic marker in patients with cardiovascular disease. In this study, the latest standard of glomerular filtration rate (GFR) calculation, that is the modification of diet in renal disease (MDRD) study equation, is used to measure the difference in the outcome of coronary artery bypass graft (CABG) surgery in various GFR groups. Between 2000 and 2005, 1,055 patients underwent CABG surgery and were categorized into 5 groups according to the National Kidney Foundation guidelines: stage 1 = normal renal function; stage 2 = mild RI; stage 3 = moderate RI; stage 4 = severe RI; stage 5 = end-stage renal failure (excluded). Precautions were taken in RI patients to avoid perioperative hypotension, fluid overload and limited cardioplegia; cardiopulmonary bypass time was kept at a minimum by performing an essential number of grafts only. Thirty-day mortality occurred in 5 of 1,052 patients (0.48%) with no statistical difference in stages 1-4. There was increase in bleed requiring reoperation and total complications from stages 1 to 4, but it was not statistically significant. Preoperative renal dysfunction in CABG surgery patients is an important predictor of outcome. Patients undergoing CABG surgery can have acceptable results without significant increase in complications and mortality provided that risk factors are minimized perioperatively.