This study evaluates the effect of preoperative increased level of serum creatinine (Cr) on early outcomes after coronary artery bypass graft surgery (CABG). 1140 patients who underwent CABG in our center were studied. Patients with Cr >2.25 mg/dl or preoperative dialysis and who had off-pump operations were excluded. Group 1 consisted of 892 patients with normal Cr (0.5-1.2 mg/dl) and group 2 consisted of 248 (21.8%) patients with mild increased level of serum Cr (1.3-2.2 mg/dl). Patients in group 1 were younger than group 2. There were more patients with hypertension in group 2, but there were not statistically significant difference between two groups in terms of the frequency of diabetes, smoking, cerebrovascular disease and New York Heart Association (NYHA) class. Left ventricular ejection fraction (LVEF) was lower in group 2. Cardiopulmonary bypass time (CPB) was longer in group 2. Early mortality was 3.2% in group 1 and 8.4% in group 2 (P