Inability to synthetize adequate amounts of IL-2 has been suggested to be the basis of defective T-cell function following anesthesia with the operation. The present study was designed to examine the effect of anesthesia and operation on host defence mechenism. serum soluble IL-2R(sIL-2R) levels and hemo-dynamic parameters were measured in 30 patients. Patients were divided into two groups (G: general anesthesia with isoflurane, E:epidural anesthesia with bupivacaine) according to the method of anesthesia. Venous blood samples were taken before anesthesia(T1), 10 mins after induction of anesthesia(T2), 10 mins after injection of bupivacaine in epidural anesthesia(T2), 1 hour after skin incision(T3), 30 mins after completion of operation(T4), and 24 hours after completion of operation(T5). Simultaneously arterial blood pressure and heart rate were measured. Six mililiter of perip-heral blood was obtained for sIL-2R studies in plain tubes. Serum concentration of sIL-2R was measured by human IL-2 receptor ELISA kit(Boehringer Mannheim Biochemica, Mannheim, Germany). Any significant change in IL-2R level was not seen in patients under general anesthesia with isoflurane and operation. Also any significant change in IL-2R level was not seen in patients who had an epidural anesthesia with bupivacaine and operation. The results suggest that suppression of T-lymphocyte function and decrease in lymphocyte counts induced by anesthesia and operation is not due to alteration of intracellular metabolism, but due to extracellular immune depressor. And general anesthesia operation with isoflurane as well as epidural anesthesia with bupivgcaine is safe and can be selected for immunosuppressive patients.