BACKGROUND: Desflurane is a new inhaled anesthetic with the lowest blood/gas partition coefficient and enflurane is one of the major anesthetics in these days. But the effect of volatile anesthetics and the site of action on the blood vessel are still controversial. Since Furchgott (1980) discovered endothelium derived relaxing factor (EDRF) from endothelium, many investigators have studied about the relationship between the EDRF and the effect of the volatile anesthetics on blood vessels. In this study, we evaluated that the effect and the action site of enflurane and desflurane on isolated aortic rings of the rabbit. METHODS: Each of obtained thoracic aorta from rabbits (1.5~2.5 kg) was divided into 4~6 mm rings, and a half of that were denuded. All of the aortic rings were preconstricted with phenylephrine 1.5 10-7 Mole in warm organ bath filled with modified Krebs' solution, and then LNAME (inhibitor of nitric oxide synthase, 3 10-4Mole) was administered to one group of aortic rings. MB (inhibitor of soluble guanylyl cyclase, 2 10-5Mole) was administered to another one group and neither of LNAME nor MB was administered to the other group. And then enflurane (1%, 2%, 3%, 4%) or desflurane (6%, 9%, 12%) was administered to all of aortic rings. The polygraph recorded the changes of tension of aortic ring which was transmitted through the force transducer. RESULTS: It was proved that basal EDRF was released from endothelium by the fact that intact aortic rings were more constricted after LNAME or MB administration. The intact aortic rings were constricted in all concentration of enflurane and both intact and denuded rings were maintained from control tension in all concentrations of desflurane. CONCLUSION: It is concluded that enflurane in all concentrations has an endothelium-mediated vasoconstriction effect and desflurane in all concentrations has no effect on isolated aortic rings of rabbit.