With 54 cases receiving pulmonectomy as the subjects of study, observations were carried out over the period of 120 days after blood transfusion with lapse of time, for the purpose to determine the liver functions in those patients by means of Paul-Bunnell test, cold hemagglutination, chick cell hemagglutination, monkey cell (Macaca rhesus erythrocytes) hemagglutination, and the correlation between the each hemagglutination reaction and the serum transaminase level was studied. The results are briefly summarized as follows. The transient rise of cold hemagglutination titer and the elevation of serum transaminase level occured concomitantly especially in the incubation period. After the onset of the desease, the rise of cold hemagglutination titer was also observed in relation to the elevation of serum transaminase level. However, the rise of cold hemagglutination titer here which is due probably to viremia was less than that in the incubation period. Paul-Bunnell reaction revealed no remarkable difference between the titers in the incubation period and after the onset. Either chick cell hemagglutination reaction or monkey cell (Macaca rhesus erythrocytes) hemagglutination reaction showed no remarkable elevation in relation to serum transaminase.