Antigenicity of ribosomal protein in Ehrlich ascites tumor and the biochemical characters were studied. The cytotoxic activity of immunized male dd-mice serum globulin was proved
by cell culture test. Ribosomal protein was moved electrophoretically to basic side than that of serum γ-globulin, and the protein concentraticn was adequate for maximal antigenicity 1 mg per mouse. The antitumor activity of immunized εerum globulin was most elevated at 25 th day after immunization, and that of lymph nodes and spleen were at 10 th day. The antitumor activity of immunized serum globulin was mainly existed in γ-globulin fraction, but also contained in α-and β-globulin fraction.