We investigated whether the polymerase chain reaction (PCR) performed with aspirates of bone marrow or lymph node can be used as a test of cure of visceral leishmaniasis (VL). Sixty-one VL patients who had received supervised treatment with sodium stibogluconate in the health centre of Médecins sans Frontières (MSF) Holland in Um-Kuraa, eastern Sudan, were studied. Immediately after treatment, no parasite could be demonstrated by microscopy in aspirates of bone marrow or lymph node. In contrast, PCR detected Leishmania deoxyribonucleic acid in 50 of the 61 lymph node aspirates (82%). Forty-nine patients were examined 3 and 6 months later; the other 12 were reported to be alive but had left the area. With 10 of these 49 patients, the PCR was negative and the patients remained free from signs and symptoms of VL; they were apparently cured. Of the 39 patients with a positive PCR after treatment, 14 (36%) developed post kala-azar dermal leishmaniasis and 9 (23%) had a recurrence of VL symptoms with reappearance of parasites in the aspirates. Four relapsed patients subsequently died of VL. We concluded that the PCR on lymph node aspirates can be used to assess treatment and cure of VL. The fact that 23 of 49 patients who received standard supervised treatment were not completely cured indicated that there is a need to investigate extended or alternative treatments.