Rabbits were immunized with Ehrlich ascitic tumor cells by intravenous injections or intramuscular injections of Freund's adjuvant. Rabbits were bled periodically, with the antisera being separated from the blood. Using these sera, the γ-Globulin titre was examined by paper-electrophoresis, anaerobic glycolysis with Warburg's manometry, and for life prolongation studies by neutralization. I wanted to know whether the antisera contained the antitumor antibody or not. 1. After immunization, the γ-Globulin titre in rabbits sera increased, with the Albumin titre decreasing. In the once intravenously injected group, such change was insignificant, but remarkable in the groups injected 3 or 6 times. In the adjuvant group, almost identical change occurred as in the latter two groups. 2. The inhibitory action of antisera on anaerobic glycolysis of tumor cells was weak in the groups injected 3 or 6 times. The antisera of the adjuvant group also had strong inhibitory action for a long duration following slow initiation. 3. Antisera of the once intravenously injected group were ineffective in the neutralization test. But in the groups injected 3 or 6 times and in the adjuvant group, it was very effective, resulting in life prolongation of the mice. 4. The peak of the γ-Globulin titre preceded the peak of glycolysis and neutralization in the group injected 6 times, whereas in the adjuvant group, peaks of the three coincided.