AIDS: Leishmaniasis, a group of syndromes caused by a number of species of the dimorphic protozoa Leishmania, is discussed in terms of its pathogenesis, natural history, and clinical presentation as influenced by AIDS. The various types of leishmaniasis can affect many areas of the body and have numerous different clinical manifestations, but primarily appear as cutaneous or visceral forms of disease. People with HIV infection are at higher risk of contracting leishmaniasis if they travel to endemic regions, or participate in high risk behaviors such as needle sharing and male homosexual sex. The diseases are usually transmitted via a disease vector, such as a sandfly, or via contact with a disease reservoir, such as infected dogs or rodents. Immunologic impairment caused by HIV infection leads to four major characteristics for HIV-associated leishmaniasis: (1) parasitic dissemination, (2) atypical locations, (3) a chronic and relapsing source, and (4) poor response to standard therapy. Diagnostic tools vary for different forms of leishmaniasis, but the standard is isolation or identification of the parasite from appropriate tissue. Newer genetic and immunologic techniques may also be useful in diagnosis. Agents used to treat leishmaniasis are antimonials, pentamidine, and therapeutic combinations, including allopurinol and interferon-gamma. Treatment of relapse and prophylaxis are discussed.