Blood Group related antigens Lewis A, Lewis B, CA 19-9, and sialyl SSEA-1 were examined in normal human skin and oral mucosa, using monoclonal antibodies to the respective antigen immunohistochemically. These antigens were not expressed on normal keratinocytes but Lewis A and Lewis B were expressed on oral mucous epithelium. Lewis A, Lewis B, and CA 19-9 were expressed clearly on intraepidermal and dermal eccrine duct, but sialyl SSEA-1 was poorly expressed in some cases. In secreting portion of eccrine gland, Lewis A was expressed in 20%, Lewis B was expressed in 70%, and CA 19-9 was expressed in 10%, and sialyl SSEA-1 was expressed weakly in 20% of cases. It's noteworthy that sialyl SSEA-1 was expressed on dendritic cell in epidermis and some infiltrated small round cell in dermis. There is no correlation between patient's peripheral blood type (Lewis) and expression of Lewis antigen in normal skin.