Observing erythrocyte agglutination reaction mainly in infectious hepatitis and with considerations of the correlation between sheep and rabbit erythrocyte agglutination and of absorption test, the following results were obtained. 1. In infectious hepatitis, the agglutination titer for rabbit erythrocyte agglutination reaction exhibited fairly high value and appeared to be almost paralled with that for sheep erythrocyte agglutination reaction. In this experiment, however, it seemed to be difficult to argue on the presence of Forssman-antibody. 2. The erythrocyte agglutination reaction with trypsin modified sheep erythrocytes showed fairly high titers in infectious hepatitis and even in other diseases compared with the agglutination titers for sheep erythrocyte agglutination reaction (Paul-Bunnell reaction). But, the alteration of these titers were approximately in proportion to those of Paul-Bunnell reaction. 3. In the absorption test of the sheep erythrocyte agglutination reaction in infectious hepatitis, the absorptions for boiled guinea pig kidney, guinea pig liver, bovine and sheep erythrocyte were quite variable and irregular. But, in a fairly number of cases of infectious hepatitis, moderately increased absorptions for guinea pig kidney and bovine erythrocytes were observed. In view of the alteration of the absorptions, during the periods of infections, the difference of the nature of the antibodies in infectious hepatitis and normal sera was predicted.