The purpose of this study were to investigate the changes in serum SGOT, CK and CK-MB levels and the significance of these changes during general anesthesia for open heart surgery. Fourteen patients, who had open heart surgery at Kyungpook National University hospital, were chosen at random their serum SGOT, CK and CK-MB levels were recorded before anesthesia(control group), pre cardiopulmonary bypass, during cardiopulmonary bypass and in the recovery room. The results were as follows: The serum SGOT levels were 21.83±4.91 IU/L, 27.20±11.83, 34.81±16.60 and 72.58±37.77, respectively. They very significantly increased (p<0.01) during cardiopulmonary bypass and recovery room compared with pre anesthesia. The serum CK levels were 58.07±6.31 IU/L, 91.79±44.58, 141.93±66.55 and 347.43±84.61 respectively. They significantly increased (p<0.05) at pre cardiopulmonary bypass, very significantly increased(p<0.01) during cardiopulmonary hypass and recovery room compared with the preanesthesia. The serum CK-MB levels were 0.00 U/L, 4.54±11.80, 14.66±17.61 and 80.07±34.72 respectively. They very significantly increased(p<0.01) during the cariopulmonary bypass and recovery room.