A 67-year-old housewife had polymorphous eruptions with tense bullae on the extremities and upper trunk. Erosions were noted on the oral and esophageal mucosa. A skin biopsy showed subepidermal blistering with linear deposition of IgG and C3 at the basement membrane zone. In addition, intercellular deposition was observed at the lower part of the epidermis. On the basis of clinical and histological features, a diagnosis of bullous pemphigoid (BP) was made. After she was treated with prednisolone, the whole-skin lesions soon disappeared. An esophageal biopsy showed intercellular deposition of IgG and C3. Indirect immunofluorescence testing using esophageal mucosa of guinea pigs showed the same deposition at the titer of 1:20. Immunoblottings with this patient's serum revealed no reactions with either BP or pemphigus antigens. Her serum reacted strongly with a 190-kD protein, the nature of which was unknown. A treatment with ciclosporin was added to this steroid therapy, and the mucosal lesions improved gradually.