The effect on the indication sensitivity of the level of antigenic sensitization of erythrocytes, molecular parameters of sensitin and of the antigen determined was revealed on various models of agglutinates and antigens determined with the aid of erythrocyte deaggregation reaction (EDR). By its dependence on the EDR sensitivity from the hemosensitization level this reaction was analogous to the passive hemagglutination inhibition test described earlier. Specific deaggregation activity of the antigens depended on their molecular parameters in the same way as their specific agglutinating activity in respect to the erythrocytic antibody diagnostic agents--both of these properties were more intensive in larger antigenic molecules.