Vesicles and bullae developed in 6 patients with psoriasis while undergoing therapy for their psoriasis. Skin biopsy specimens were taken from their lesions and studied for regular histopathologic findings and direct immunofluorescence. These studies confirmed that they had coexistent psoriasis and bullous pemphigoid. A review of the therapy that the patients were given incriminates anthralin, crude coal tar, UV light and salicylic acid, the possible cause of the development of their bullous pemphigoid lesions.