Electrophoretic patterns of certain sera from rabbits immunized intravenously with streptococcal vaccines exhibit discrete protein bands in the γ-globulin region. These were identified as group-specific carbohydrate antibodies. The L-chains of these γ-globulins exhibited electrophoretic homogeneity. This report describes a group B immune serum which possesses unusual cryoprecipitating properties. Ninety per cent of the γ-globulin was cryoprotein and was distributed in two electrophoretically distinct peaks designated fast and slow. Both proteins, isolated by electrophoresis were γG-globulin. The slow cryoglobulin possessed group B antibody activity. Although the fast cryoglobulin agglutinates group B cell walls the exact specificity has not been determined. Electrophoretic patterns of dissociated light chains were studied by a variety of electrophoretic techniques. By disc electrophoresis in acrylamide gel the L-chains of the slow cryoglobulin were heterogeneous and exhibited six bands. L-chains of the fast cryoglobulin were distributed in only two bands. These data suggest that immunization has resulted in the proliferation of a limited population of lymphoid cells which produced γ-globulin with cryoprecipitating properties.