Epidermolysis bullosa acquisita (EBA) of the immunopathological type is a distinct disease entity which we propose to name dermolytic pemphigoid. Clinical features of this disease are heterogeneous. An inflammatory phase may mimic bullous pemphigoid or, less commonly, mucosal pemphigoid or dermatitis herpetiformis. The noninflammatory mechanobullous phase equates with classic EBA and features marked skin fragility, bullae and/or erosions at sites of trauma, which result in scarring and milia. The inflammatory or the noninflammatory phase may occur separately or in combination. Transition from inflammatory to noninflammatory phases has been seen. Linear basement membrane zone (BMZ) immune deposits of immunoglobulin G (IgG) are present in the lesional and uninvolved skin of affected patients by immunofluorescence and are essential for the diagnosis. Many patients also have circulating antibasement membrane zone IgG antibodies. Immunoelectron microscopy localizes the immune deposits in the lamina densa and sublamina densa zone and serves to distinguish this disease from diseases with lamina lucida antibodies, such as bullous pemphigoid and mucosal pemphigoid. The EBA antigen has recently been identified and partially characterized from human skin using circulating antibasement membrane zone antibodies from patients with EBA. The EBA antigen consists of 2 components of Mr 290,000 and 145,000, and were shown to be distinct from other known basement membrane components. Mouse monoclonal antibody, H3a, recognizes the same 290 kilodaltons (kd) and 145 kd proteins and localizes to the lamina densa and sublamina densa zone of human skin. The EBA antigen is a newly recognized basement membrane component that is restricted in its distribution to the BMZ of stratified squamous epithelium of both keratinizing and nonkeratinizing types.