A 65-year-old man with stage I testicular seminoma, treated with surgery and radiation, had fever of unknown origin, adrenal insufficiency, and an isolated perianal ulcer. Tissue diagnosis of disseminated histoplasmosis was established by biopsy of the perianal ulcer, an unusual cutaneous manifestation of the disease. Treatment with amphotericin B resulted in rapid clinical improvement and complete healing of the perianal ulcer.