Antigens specific for discrete segments of the intestinal tract of germ-free rats have been identified. There is at least one duodenum-, one ileum- and one colon-specific antigen. In addition there is an intestine-specific antigen present at all levels of the bowel. The intestine-specific antigens are found in the goblet cell mucus. The intestinal epithelial cell cytoplasm contains antigen which is shared by other tissue.