Pemphigus foliaceus induced by ionizing radiation therapy is a rare condition. We describe the case of a 70-year-old female who developed pemphigus foliaceus after X-ray treatment for an adenocarcinoma of the left breast. The eruption started at the portal of irradiation and only subsequently spread to other cutaneous areas. Mucosal membranes were not affected. Skin lesions were completely responsive to dapsone therapy.