In an attempt to study auto-immune phenomenon in the course of development of chronic hepatitis, the sensitization with homologous liver and Freunds complete adjuvant as well as the passive transfer of sensitized spleen cells were conducted with rats. As a result it was found that by the sensitization with homologous liver and Freunds complete adjuvant a marked round cell infiltration and the stellate cell reaction were observed in Glissons capsule and sinusoid of the liver as compared with control group, and with a few cases there was observed lymphoid focus in Glissons capsule. By the passive transfer of sensitized spleen cells, there could be detected the infiltration of round cells in Glissons capsule and sinusoid of the liver and in a few cases liver cell necrosis mainly of piecemeal necrosis. In the subsequent observations on blood anti-liver antibody, intratissue γ-globulin as well as the localization of anti-liver antibody, there could be recognized no significant corre lations to the above-mentioned histological changes of liver, but in the culture of sensitized rat peripheral lymphocytes conductes in the presence of liver antigen there was observed a significant blast-like transformation as compared with control group. From these experimental results with rats it seems that the lymphoid focus and piecemeal necrosis observable in Glissons capsule of the liver in human liver diseases can also be said fairly safely to be the histological expression of auto-immune phenomenon.