[en] A 79-year-old man was admitted to our hospital for radiation therapy for lung cancer on July 24, 1984. In the course of radiation therapy, many bullas were recognized on his trunk. The lesion was diagnosed as bullous pemphigoid. To date, about 27 cases of malignant tumor with bullous pemphigoid have been reported in Japan. At present, the causal relation between malignant tumor and bullous pemphigoid has not been established. In our case, the bullous lesions disappeared during the course of radiation therapy, and the patient has been in good general condition for nine months without recurrence or metastasis of lung cancer. (author)