Sevoflurane degradation by carbon dioxide absorbents during low flow anesthesia forms the haloalkene compound A, which causes nephrotoxicity in rats. Numerous studies have shown no effects on postoperative renal function after moderate (3-4 hours) low flow sevoflurane, anesthesia. However, effects of longer exposures remain unresolved. We compared renal and hepatic functions after long duration low flow (1L/min) sevoflurane and isoflurane anesthesia in ASA I or II surgical patients. Sevoflurane (n=30) and isoflurane (n=30) groups were similar with respect to age, sex, height, weight, ASA status and anesthetic duration and exposure. There were no significant differences between anesthetic groups in first, second, and third postoperative days regarding blood urea nitrogen, serum creatinine, serum aspartate aminotransferase, serum alanine aminotransferase, serum total bilirubin, serum alkaline phosphatase , or serum lactate dehydrogenase. Also there were no significant differences between anesthetic groups regarding the 24 hours urinary (creatinine, protein, albumin or glucose) in the 3 postoperative days. Although proteinuria, albuminuria and glucosuria were common in both groups.This study concluded that no specific toxicity on the kidney and liver was observed in surgical patients following long duration low flow sevoflurane anesthesia and that the effect of prolonged low flow sevoflurane anesthesia on postoperative liver and kidney function was the same as that of prolonged low flow isoflurane anesthesia.