Experiments on male hybrid mice demonstrated that specific immunotherapy with preparations based on carcinoembryonal antigen and mucin containing CA 125 antigen was not associated with general toxicity, local irritating effect, and hepatorenal dysfunction. The absence of toxicity is apparently due to the fact that antigens injected intramuscularly or subcutaneously virtually do not enter the blood. Injections of preparations based on carcinoembryonal antigen and mucin containing CA 125 antigen to mice induced a standard immune response with predominance of class M immunoglobulins during the early terms and class G immunoglobulins at later terms.