Traditionally, the mainstay of visceral and diffuse cutaneous leishmaniasis therapy has been pentavalent antimony, with pentamidine and amphotericin B reserved for refractory cases. Interferon-gamma (IFN-gamma) in combination with pentavalent antimony has been used successfully in treating patients refractory to pentavalent antimony and in patients with previously untreated visceral leishmaniasis (39 total). In addition, 6 patients with diffuse cutaneous leishmaniasis have been treated with combination IFN-gamma and antimony therapy. Preliminary experience with these patients indicates that IFN-gamma is a useful adjunct therapy for severe or refractory cases of visceral leishmaniasis; however, the potential of IFN-gamma in treating diffuse cutaneous leishmaniasis cannot be assessed as current clinical experience is too limited.