The architecture and the plasticity of the dermo-epidermal interface of normal and pathological human skin have been studied by scanning electron microscopy. Biopsies were incubated in a sodium bromide solution to dissociate the epidermis from the dermis. The cleavage plane was located at the level of the lamina densa of the basal membrane as evidenced by optical and transmission electron microscopy. The surface on either side has digital projections, presenting on the epithelial side the relief of the basal cells and on the dermal side the complementary architecture. The highly folded basement membrane can be considerably stretched and its architecture can be modified by two processes. A passive type results from movement transmitted to the basement membrane in response to mechanical stress. An active type, depending upon metabolic remodelling, is illustrated by the dermal downgrowth of basal cell carcinoma.