Objective. Evaluation of perioperative renal function is very important for early diagnosis and treatment of acute kidney injury after coronary artery bypass grafting. Serum creatinine levels, creatinine clearance, and estimated glomerular filtration rates used in determination of postoperative kidney injury can lead to late detection. Therefore, it is necessary to make a diagnosis earlier in clinical practice and to search for a reliable method. The reliability of the use of serum neutrophil gelatinase-associated lipocalin levels in close follow-up of renal function was evaluated in patients with coronary artery bypass grafting under cardiopulmonary bypass in our study. Patients and Methods. A total of 40 patients who underwent coronary artery bypass grafting under cardiopulmonary bypass between September 2009 and February 2010 were included in the study. The reliability of the postoperative 1st day plasma neutrophil gelatinase-associated lipocalin (Triage (R) NGAL Device; Biosite Inc.) measurements was evaluated in kidney injury developed in the first 5 days after operation that was detected using the Risk-Injury-Failure-Loss-End stage criteria. Results. Ten (25%) women and 30 (75%) male patients were included in the study. The average age is 59 +/- 8.6 years. Kidney injury according to Risk-Injury-Failure-Loss-End stage criteria developed in 8 patients (20%). For 150 ng/mL cutoff value of postoperative plasma neutrophil gelatinase-associated lipocalin levels, the area under the receiver-operating characteristic curve was 0.965. Neutrophil gelatinase-associated lipocalins sensitivity, specificity, and negative and positive predictive values were 100%, 93.8%, 100%, and 80%, respectively. Conclusion. It has been determined that plasma neutrophil gelatinase-associated lipocalin levels can be reliably used for early diagnosis of kidney dysfunction in patients undergoing coronary artery bypass grafting.