The collagen fiber network of rabbit palatine tonsils was studied by scanning electron microscopy (SEM) of alkali-water macerated tissues. Tissue sections adjacent to the SEM specimens were also observed by light microscopy. The collagen fibers, which consisted of collagen fibrils, branched out or fused together, thus forming the collagen networks as a whole. The collagen networks within the follicles were coarse, while those within the interfollicular areas were dense. The interfolliculae area that surrounded or was adjacent to the follicle had dense networks arranged in a concentric pattern around the follicles. Such a dense collagen network may be the site in which lymphocytes actively migrate. In the interfollicular area, there were high endothelial venules (HEVs) and lymphatic vessels which were surrounded by collagen sheaths. These venules and lymphatic vessels had many pores through which the lymphocytes appeared to migrate. Transmission electron microscopy of lead-stained tissue samples showed that the reticular fibers were closely associated with the thin cytoplasmic processes of the reticular cells. These processes were in direct contanct with the lymphocytes and had many pores or fenestrae.