The authors convened an electron microscopic study of the interaction of lymphocytes in the peripheral blood of schizophrenic patients with the brain cells of the embryo after a 24-hour joint cell incubation. It was found that in comparison with the lymphocytes of the normals, the lymphocytes of schizophrenic patients much more frequently come into contact with the cells of the brain culture. The lymphocytes of the patients are characterized by an increased amount of cytoplasmatic processes. A maximum amount of lymphocytes which came into contact was seen in experiments on population enriched in activized cells of the lymphocyte in schizophrenic patients. It is particularly the activized lymphocytes of schizophrenic patients that coming into contact called forth degenerative changes in the cells of brain culture in the area of contacts.