The expression of Lewis antigens is thought to be controlled by the Secretor and Lewis genes. While secretor status is known to regulate the expression of ABH antigens in many tissues, few studies have attempted to correlate Lewis antigen expression on erythrocytes and saliva with that of epithelial tissues. We examined the expression of Lewis a and b and related antigens in human epithelium of minor salivary glands and labial nonkeratinized oral mucosae from 16 individuals by immunohistology using monoclonal antibodies. The expression of these antigens, as detected by monoclonal antibodies (MAbs) used, was correlated with erythrocyte phenotype and saliva secretor status. In acinar cells of glands, Leb antigen was expressed only in secretors, and Lea only in nonsecretors. However, in gland ducts and oral mucosae, Leb was found in both secretors and nonsecretors, as well as in 2 cases of Lea-b-, secretors. Thus, antigen expression in acinar cells of minor salivary glands was correlated with the predicted genotypes, whereas inappropriate expression of Leb antigen was found in epithelial cells of gland ducts and oral mucosae. The present data indicate that the Lewis blood group phenotype is regulated differently in duct cells and stratified epithelium than in saliva and erythrocytes.