An elderly man presented with a chronic exfoliative erythroderma of unknown etiology. Skin biopsy suggested mycosis fungoides. After mucous membrane and cutaneous ulcers developed, Histoplasma capsulatum was cultured from skin and bone marrow. It was also identified on histopathologic examination. We know of only two other similar cases reported in the literature and suggest that idiopathic or confusing cases of exfoliative erythroderma, with or without ulceration, be evaluated for histoplasmosis.