BACKGROUND Reduction in organ function is a common problem in the perioperative period of the elderly patient. Especially renal function is often decreased in this situation. PATIENTS AND METHODS In a prospective study, we assessed the perioperative changes of renal function in elderly (> 65 years, n = 30) and younger (< 65 years, n = 30) patients without preoperative renal dysfunction who were scheduled for major abdominal surgery. After induction of anesthesia (t0), at the end of surgery (t1), 4 h after surgery (t2), and on the first (t3), second (t4) and third postoperative day (t5), alpha-1-microglobulin, beta-N-acetyl-glucosaminidase, fractional sodium clearance, and creatinine clearance were measured. RESULTS The creatinine clearance was significantly higher at all time points in the elderly than in the younger patients (p < 0.05). Fractional sodium clearance showed no significant differences between the two groups. At t4 and t5, alpha-1-microglobulin had increased significantly from the baseline value only in the elderly patients. Beta-N-acetyl-glucosaminidase was significantly elevated compared with the baseline value in the elderly patients and also differed significantly from younger patients during the study period. CONCLUSION In elderly patients undergoing major abdominal surgery, short-term alternations in the renal system were observed in the perioperative period. With adequate volume replacement, no relevant disturbances in renal function are to be expected in the elderly surgical patient.