OBJECTIVE Renal function declines with age, but little is known about the renal effects of the inhaled anesthetic sevoflurane in the elderly. We therefore compared the renal effects of sevoflurane and isoflurane anesthesia in elderly patients. METHODS Thirteen patients aged > or =70 years undergoing gastrectomy with epidural anesthesia combined with general anesthesia were randomly assigned to receive either sevoflurane ( n = 7) or isoflurane ( n = 6). Dopamine (3-5 microg.kg(-1).min(-1)) was administered to all patients. Blood and urine samples were collected before, during, and after anesthesia. Serum and urinary inorganic fluoride was measured, and renal function tests were performed. RESULTS Serum inorganic fluoride was significantly elevated in both groups. The production of inorganic fluoride was significantly greater in the sevoflurane group, but the level did not exceed 50 micromol.l(-1) in any patient. No abnormalities were observed in blood urea nitrogen (BUN), serum creatinine, or urine volume in either group. The albumin excretion index increased during anesthesia and decreased after anesthesia in both groups. Creatinine clearance was unchanged in the sevoflurane group but fluctuated during and after anesthesia in the isoflurane group. alpha(1)-Microglobulin (MG), beta(2)-MG, and urinary N-acetyl-beta-D-glucosaminidase (NAG) excretion increased up to 3 h after anesthesia, and alpha(1)-MG and beta(2)-MG excretion increased on postanesthesia day 3. CONCLUSIONS In both groups, glomerular and tubular function were transiently affected, but no abnormalities were found in routine laboratory tests, suggesting that neither isoflurane nor sevoflurane in combination with dopamine and epidural anesthesia seriously affects renal function in the elderly.