Liver diseases, especially epidemic hepatitis were studied, employing the Oudin's precipitation test in the agar layer. And the results were as follows. 1. The auto-antibodies corresponding to the liver and kidney antigens were observed, by the Oudin's precipitation test in the agar layer, on 9 cases of acute hepatitis, 17 cases of chronic hepatitis, 6 cases of liver cirrhosis and other diseases. In liver diseases, it remarkably reacted to the liver antigen and showed many precipitation bands, and the precipitation band became numerous with the progress of disease in order of acute hepatitis, chronic hepatitis and liver cirrhosis. On the other hand, it remarkably reacted to the kidney antigen and showed many precipitation bands, in kidney diseases. 2. Comparing each form on the classification of epidemic hepatitis with the results of the Oudin's precipitation test in the agar layer, the liver antigen remarkably reacted to the typical form, jaundiced form and influenza form and the precipitation band appeared few in the gastroenteric form, mixed form and latent form, in comparison with the former. On the other hand, the kidney antigen showed no difference on the number of precipitation band in each form of kidney diseases. 3. Comparing the number of days after the attack of epidemic hepatitis with the results of the Oudin's precipitation test in the agar layer by the liver antigen, the appearance of precipitation band was remarkably seen at 6-9th month after the attack of disease and it became more remarkable at the chronic stadium and the shifting stadium to liver cirrhosis. 4. Comparing the liver function with the Oudin's precipitation test in the agar layer, the higher the positive serum colloidal reaction (the results judged on the serum Takata's test, Gross test, Weltman's test, thymol turbidity test, cobalt chloride test, colloidal red test, cephalin-cholesterol flocculation test and cadmium test etc.) became, the more was the number of precipitation band. No correlation between the above precipitation test and the hippuric acid test was observed, but there were some correlation between the above, precipitation test and the bromsulphalein test, and the appearance of precipitation band was remarkably observed on the cases with the liver function damage. 5. As for the relation of it with the blood picture, the more the precipitation band corresponding to the liver antigen appeared, the fewer were the hemoglobin value, erythrocyte, thrombocyte, leukocyte and monocyte count, and the more were the lymphocyte and eosinocyte count. 6. As for the relation of it with the serum protein value showed the declining tendency, the albumin value on the proportional picture of serum protein showed the decreasing tendency, the α-, β- globulin value slightly showed the decreasing tendency and the γ-globulin value showed the increasing tendency.