Currently, the incidence of massive transfusions during operation has been increasing because the more complicated and invasive operations than before can be done due to enhanced technololgy in both anesthesia and surgery. In spite of marked improvement in immunology and transfusion technique, massive transfusions are associated with several problems usually not seen in normal transfusion practice. In order to evaluate the effect of massive transfusion on the serum sodium, potassium levels and platelet count in the blood during general anesthesia, we have retrospectively examined these values before and after massive transfusion in 62 patients who received at least one blood volume at Kosin Medical Center from January 1985 through May 1989. Statistical significance was assessed by using Student's t-test. The results obtained were summarized as follows; 1) The average volume of transfusion was 5432 ml (13.4 units). 2) The total number of massive transfusions was 62 (0.47%), excluding cases with renal failure or open heart surgery, out of 13,213 anesthetic patients 3) The hightest incidence of age distribution was from 50 to 59 years. 4) There were 2 fatalities (3.2%) that seemed to be due primarily to the transfused blood itself. 5) The decrease in the serum sodium concentration after transfusion was not statistically significant (p>0.05). 6) There was a statistically significant decrease in serum potassium concentration after transfusion (p<0.05). 7) The decrease in the platelet count after massive transfusion was by 44% which was statistically aignificant (p<0.05). 8) Except for the decrease in the platelet count (p<0.05), there was no statistical significance in the changes of sodium and potaasium levels (p>0.05) after massive transfusion between the shock and non-shock groups. Since massive transfusion can be associated with the decrease in the serum potassium and platelet count, these patients blood levels should be monitored during and after maseive transfusion for proper management.