Recently introduced tramadol structually similar to morphine, was a new category in analgesia. Also it was reported that that drug could be used in the shale of balanced anesthesia. So we carried out the experiment for evaluation of its effect on sympathoa-drenal system activity, indexed by plasma epinephrine and norepinephrine levels, to compare with other methods of balanced techniques in 18 Patients. Patients in group 1 who received Thalamonal-N2O-O2, patients in group 2 were given pethidine. diazepam-N2O-O2, patients in group 3 were tramadol. diase7am-N2O-O7, Venous samples were obtained before induction of anesthesia, after induction but before skin incision and immediately after skin incision. Sequential results of plasma epinephrine(pg/ml)were 62.0+16.8(mean+s.e.), 134.3+18.7, 127.3+26.2 in group 1, 65.8+13.1, 79.7+13.1, 91.3+22.5 in group 2 and 74.0+24.9, 88.0+17. 1, 108.4+23.2 in group 3. Values of norepinephrine(pg/ml) were 212.5+27.1, 167.7+23.9, 236.2+34.4 in group 1, 213.8+59.1, 162.0+33.2, 246.8+55.7 in group 2 and 236.0+39.6, 197.7+59.4, 208.4+25.6 in group 3. Those values did not differ significantly between three groups. Theae data revealed that this method of balanced anesthesia using tramadol could effectively block the sympathetic response to anesthestic and surgical stress as other method of balanced techniques.