It has been previously confirmed that hemolysin and agglutinin are produced for erythrocytes in the anti-sera of the animals receiving the antigen obtained from the rabbits sensitized with antigens extracted from various viscera. Therefore, with the purpose to study the significance of the mechanism and the in vivo reactions of hemolytic anemia the author induced in various animals by injecting these heterogenous organ antisera, and obtained the following results. 1. When rabbits are sensitized with the physiological saline solution of various organ antigens extracted from such organs as the dog liver, kidneys and spleen, a rise in the antibody titer for the liver as well as a rise in the non-specific antibody titer for the other crgans can be observed. Simultaneously an increase in the hemolysin value and agglutinin value can be recognized. 2. In observing changes in the blood picture of the dogs after the injections of the various organ antisera mentioned above, there has been recongized a picture of an acute hemolytic anemia revealing a decrease in the erythrocyte count, a decrease or a fall in Hb and Ht values, a fall in erythrocyte resistance and an increase in the reticulocyte count. 3. Although no bivalent antibodies such as hemolysin and erythrocyte agglutinin can be detected in the circulation blood of the dogs injected with various organ antisera, the erythrocyte resistance shows a marked fall for a considerably long period of time, and also the dog erythrocytes prove to be positive to direct Coombs' tests. 4. Histologically specific changes of viscera have been demonstrated in the order of the antiserum for the kidneys, antiserum for the liver, and antiserum for the spleen, showing the changes specific to each organ. At the same time the reactions of the reticuloendothelial system in the spleen, liver and lymph nodes are marked, and hemosiderosis can also be recognized, indicating the changes suggestive of in vivo hemolysis. 5. In the animals injected with organ antisera relatively specific disturbances can be recognized in corresponding organs and at the same time an acute hemolytic anemia is induced by hemolysin and erythrocyte agglutinin contained in the organ antisera as one of nonspecific changes. Moreover, it has been clarified that a mono-valent antibody plays a considerably significant role even in such an immuno-hemolytic anemia.