Epidermolysis bullosa acquisita (EBA) is an acquired mechanobullous disorder characterized by traumaticlly induced bullae in skin subjected to frictional injury, i.e., acral extensor surfaces or any point of sufficient mechanical distress. Two new patients with EBA are reported. Histopathologic findings were subepidermal bullae with sparse superficial perivascular mononuclear cell inflammatory infiltrates. The periodic acid-Schiff (PAS)—positive basement membrane zone (BMZ) was split between the floor and roof of the blisters with most attached to the blister roof. Electron microscopy of normal skin from one patient revealed a bandlike zone of granular material within the dermis immediately beneath the basal lamina. Nonbranching filaments were embedded in the granular material. Electron microscopy of normal skin from the second patient revealed a markedly diminished density of anchoring fibrils but no granular material. Immunologic findings in skin biopsies were C′3, IgG, and other immunoglobulins in varying combinations in both cases and in all reported cases. Comparisons of direct immunofluorescent (IF) findings in nine reported cases with 223 cases of bullous pemphigoid (BP) suggest that BMZ deposits of IgG plus IgA and/or IgM occur more frequently in EBA than in BP. Indirect IF studies of patients' sera revealed antibodies to the BMZ in two samples of one of our two cases and in one of seven cases reported by others. While both EBA and BP characteristically yield positive IF findings in the BMZ, clinical, electron microscopic, and some immunopathologic findings indicate that the two diseases are distinct.