The diagnosis of visceral leishmaniasis must be based upon a demonstration of the parasite in tissues of the patient. The best diagnostic test is a splenic aspirate, which is safe, highly sensitive and specific if the technique described in this paper is used and both smears and cultures of the aspirate are performed. Peripheral blood and nasal exudate have parasites in smears and/or cultures in 75 and 40% of Kenyan visceral leishmaniasis patients, respectively. Sodium stibogluconate (Pentostam) is the preferred treatment for visceral leishmaniasis. Recent Clinical Research Centre trials of different schedules of treatment with sodium stibogluconate are discussed. Currently, we recommend sodium stibogluconate, 20 mg/kg once daily for 30 days, for initial treatment. For patients who have not responded to initial treatment with sodium stibogluconate or have relapsed after initially responding to this treatment, we recommend sodium stibogluconate, 20 mg/kg once daily for 60 days. Further studies are now underway comparing the combination of allopurinol plus sodium stibogluconate versus sodium stibogluconate alone for unresponsive or relapsed patients.