The livers can influence the distribution of the thyroid hormones between the intrace-llular and extracellular compartments, In order to evaluate the changes of liter function following thyroid surgery, 52 patients were chosen at random and divided into 4 groups i.e. 1) Thyroid cancer group, 2) non toxic nodular goiter group, 3) the group treated with T3 and T4, and 4) the group net treated with T3 and T4. The values of SGOT and LDH isoensrmes were measures before operration(control va lues), 1 day and 3 dars after operation. We analyzed the results according to anesthetic agents. The results were as follows : In the patients recieving halothane, the values of SGOT was 24.31±9.05 U/l at control. Those at 3 days after operation were 30.35±11,65 U/l (P<0.05) . The Values of LDH5 were 5.36±3.31% at control, 8.24±3. 80 at 1 day, 7.32±0.09% at 3 darts(p<0.75). In the group treated with T3 and T4, the values of_SGOT were 23.82±8.91 U/l at control, 37.84±13.51 U/l at 3 days(p<0.05). The values of LDH5 were 3.89±2.89% at control, 8.06±4.13 at 3 dara(P<0.05). In other groups in cluding these patients recieving enflurane, postoperative SGOT, SGPT and LDH isoengrmes levels were insignificant compared with preoperative value.