Leishmaniasis, while uncommon in the United States, is found frequently in other parts of the world. We present a case of cutaneous leishmaniasis and describe diagnosis, clinical and histological characteristics, and treatment. Report of a Case A 45-year-old man vacationed with his wife on the Yucatan Peninsula in Mexico in March 1975. Approximately nine days after leaving, they both noticed that "bites" on the arms had evolved into crusted papules. The man, the more symptomatic of the two, was seen by one of us (M.K.) in August 1975. A biopsy specimen showed a focus of marked ulceration in which the upper portion of the dermis and connective tissue were completely replaced by amorphous eosinophilic material. The dermis showed various-sized aggregates of histiocytes and multinucleated giant cells that were surrounded by a moderate to sharp infiltration of lymphocytes. Also in the dermis were well-marginated tubercles, some of which were obscured by