A specific monoclonal antibody against sulfatides was used to examine the cellular localization of sulfatides, the most predominant acidic glycosphingolipids in both rabbit and human gastric mucosa. The monoclonal antibody selectively recognized sulfatides among the acidic glycolipids extracted from rabbit gastric mucosa. Immunofluorescence staining revealed that specific staining was localized in the epithelial cells of the stomach. Both epithelial and glandular cells were stained in the fundic mucosa. In human stomach, the staining pattern was essentially identical to that in rabbit stomach. The specific localization of sulfatides in the epithelial lining supports our hypothesis that they may be a component of mucosal defensive substances and an adhesion receptor for Helicobacter pylori.