We describe a patient who developed an exclusively perianal-intergluteal vesicular eruption after receiving a course of ampicillin/sulbactam. Direct immunofluorescence microscopy of perilesional skin demonstrated linear deposits of IgA along the dermal-epidermal junction. Circulating IgA autoantibodies against the 120-kd soluble ectodomain of bullous pemphigoid antigen 180 (LAD-1 autoantigen) were detected by immunoblotting. Discontinuation of the antibiotics resulted in a rapid resolution of the skin lesions. This is a most unusual case of localized drug-induced linear IgA disease.