Summary: Electrophoretic analyses in a Tiselius apparatus have been made of several antipneumococcal horse sera and of concentrates produced from them. In every instance the antibody lay in the γ-component. Thus though pneumococcal horse antibodies are for the most part larger than the molecules of normal γ-globulin they display essentially the same electrical behavior. Unsuccessful attempts were made to resolve antibody and γ-components by the prolonged electrophoresis of a serum both diluted and undiluted and by electrophoresis at different pH values. Measurements of areas on Longsworth's electrophoretic diagrams of sera before and after absorption with specific polysaccharides demonstrate that antibody-content estimated in this way agrees well with that determined chemically.