We examined the influence of sevoflurane and isoflurane anesthesia on renal function in elderly patient who underwent gastrectomy. Plasma inorganic fluoride level was significantly higher in sevoflurane group compared with isoflurane group from 3 hours after the beginning of anesthesia to the 3rd operative day. In contrast, parameters such as urinary beta 2 microglobulin, urinary N-acetyl-beta-D-glucosaminidase, and urinary gamma-GTP activities increased in both groups, but the increase was not significant. Serum BUN and creatinine levels were within normal limits. These results suggest that elderly patients without renal dysfunction appear unlikely to have any significant problem after prolonged sevoflurane anesthesia.