We assessed the effects of sevoflurane and enflurane, i.e. halogenated volatile anesthetics, on blood pressure, heart rate, and renal sympathetic nerve activity (RSNA) in rabbits. To eliminate the influence of baroreceptor reflex, bilateral carotid sinus nerve branches and vagus nerves were resected before the measurements. Sevoflurane and enflurane [0.5-1.15 MAC (minimum alveolar anesthetic concentration)] did not significantly change heart rate, but decreased mean blood pressure in a concentration-dependent manner. On the other hand, while sevoflurane did not significantly attenuate RSNA, enflurane decreased it in a concentration-dependent manner. There was a significant difference between sevoflurane and enflurane in their effects on RSNA. These results suggest that a decrease in blood pressure caused by sevoflurane is related to factors other than sympathetic nerve activity, and that hypotension caused by enflurane is related more closely to attenuated activity of sympathetic nerve, at least, in comparison with sevoflurane.