Background : There are many documents about the hemodynamic changes during sympathetic block- ade produced by epidural anesthesia, but few reports have addressed the effects of epidural anesthesia on renal blood flow and function. We evaluated the effects of epidural anesthesia on renal function in patients undergoing total abdominal hysterectomy with general anesthesia. Methods : Thirty patients were randomized to groups I (n = 15) or II (n = 15). The epidural catheter was inserted via 17 gauge Tuohy needle through the L2-L3 intervertebral space of the patients in both groups, only in group II, the patients received 15 ml of 0.125% bupivacaine. All the patients were anesthetized with enflurane, nitrous oxide and oxygen. We measured mean arterial pressure and urine output, creatinine clearence, Na clearence, fractional excretion of Na and free water clearance during operation and compared the data between the two groups. Results : Mean arterial pressure was lower in group II than in group I (P < 0.05), but other data were not different significantly between the two groups. Conclusions: Renal function was maintained even though epidural anesthesia reduced mean arterial pressure. (Korean J Anesthesiol 2000; 38: 278~282)