The specificity of the immunoelectroadsorption technique (IEA) was studied. When S. mansoni antigen was used, all specimens from patients with schistosomiasis and serum from persons with other diseases or disorders gave strong reactions in the IEA test. The IEA and passive hemagglutination techniques were compared under identical conditions with a hapten-antihapten system. Regardless of whether S. mansoni or a hapten were used as antigens, increases in the protein concentration of a given sample by the addition of gamma globulin resulted in progressive increases in optical thickness of the IEA. In contrast, no noticeable increase occurred when albumin was added to the sample. The hemagglutinating titers were directly related to the concentration of specific antibodies present in a given sample and were not affected by the addition of albumin or gamma globulin. The results obtained with IEA showed that there was a direct relation between optical thickness and globulin concentration in a given sample. No specific anti-S. mansoni or dinitrophenyl antibodies were detectable by the IEA technique, therefore indicating that this technique is not satisfactory for determining antigen-antibody reaction in parasitic diseases.