A total of 153 regional lymph nodes obtained from 50 patients, operated for gastric, lung, breast, colonic and cervical cancers, were studied. Immunohistochemical methods were used to detect different markers and enzymes (CD1, CD2, CD3, CD4, CD8, CD20, CD30, CD35, CD45, l light Ig chain, lysozyme (muramidase), a-1-antichymotrypsin, protein S100 and FVIIIR). Results indicate that failure of local immunity is explained by the followings: 1. decrease in the total number of T-cells (suppressors as well as helpers); 2. high number of B-cells, plasmoblasts and antibody-forming plasmocytes, know to be able to block the cytotoxic T cells; 3. decrease in the number of incoming free phagocytes of monocytic origin and reduction in the phagocytic activity of fixed macrophages (sinus histiocytes); 4. high functional activity of dendritic reticulum cells; 5. non-handled stimulation 6. reduction in area of postcapillary venules and impairment of lymphocyte recirculation through them.