Plant lectins are known to have potent biological actions of normal and malignant cells. High concentrations of these lectins are present in many types of high residue diets. The specific binding of wheat germ agglutinin, a dietary plant lectin, to N-acetylglucosamine was used as the basis for purification of this lectin by biospecific chitin affinity chromatography. Subsequently, methods were developed for the extraction, purification, and identification of wheat germ agglutinin from fecal samples. Biologically intact wheat germ agglutinin was detected in ileostomy effluent and fecal collections from human subjects consuming a diet containing wheat germ. These studies demonstrate that wheat germ agglutinin can traverse the human small intestine intact. It is feasible that orally ingested wheat germ agglutinin and other plant lectins which interact with a wide variety of cell membranes may alter intestinal epithelial or bacterial cell function in the human bowel.