An immunohistochemical investigation of beta1,4-galactosyltransferase (beta1,4-GalT) on human skin tissue was performed on formalin-fixed paraffin-embedded sections using a monoclonal antibody, MAb8628, which specifically recognizes a protein moiety of human beta1,4-GalT. Distribution of the galactose beta1,4-N-acetylglucosamine (Gal beta1,4GlcNAc)-R epitope was also detected by staining with Ricinus communis agglutinin (RCA) 120. The beta1,4-GalT was observed to be localized at the perinuclear region of epidermal keratinocytes. The fine localization was also observed at the supranuclear region in the cells of apocrine glands, eccrine ducts and glands. The positive staining with RCA 120 was well colocalized with the cells expressing the beta1,4-GalT. An electron microscopic study revealed that positive signals of beta1,4-GalT definitely reside in the Golgi apparatus. No immunoreactivity was observed in any other intracellular structure or on the cell surface. These findings strongly indicated that the beta1,4-GalT is the major enzyme responsible for the Gal beta1,4GlcNAc-R epitope synthesis in human skin tissue.