SUMMARYMonoclonal antibodies to human α1‐microglobulin (α1‐m), a glycoprotein present in most biological fluids, reacted with the basement membrane of the epidermo‐dermal junction and that of eccrine sweat glands in normal human skin. This immunofluorescence was specific in that control antibodies of known well‐defined reactivity did not stain these structures. Therefore, α1‐m seems to be a new antigenic component of the junction and it may be an interesting antigen to study in diseases