The presence or absence of a basement membrane at the epidermal-dermal junction has been, and probably will remain, problematical. That a periodic-acid-Schiff (PAS)-positive zone occurs at the epidermal-dermal junction is undoubted; whether this actually is a basement membrane is questionable. This zone, or membrane, definitely has some characteristics of a basement membrane. The purpose of this project was to study the PAS-stained membrane in a number of skin lesions and was an attempt to determine whether it was truly a basement membrane and even if not, whether its character, its presence, or absence could be of any use in diagnostic histopathology of the skin. Herxheimer, in 1916, using Mallory's connective tissue stain, studied the problem of the epidermal basement membrane and concluded that there was present, immediately below the basal cells of the epidermis, a thin fiber 0.5μ in diameter which was morphologically