When the polymerase chain reaction (PCR) was used to test lymph-node aspirates from 35 patients from eastern Sudan, who had had visceral leishmaniasis but were believed cured, leishmanial DNA was detected in samples from 14 of the patients. There were no significant differences between the PCR-positives and -negatives in terms of age, sex, spleen size, malaria status or presence of anti-Leishmania antibodies. However, PCR was more often positive in the patients who tested negative by the leishmanin skin test (LST) than in those who gave positive skin tests. Moreover, patients with a positive PCR and a negative LST converted more often to LST positivity than those with a negative PCR and a negative LST. The most important finding was that, during follow-up, eight (57%) of the PCR-positives, but none of the 21 negatives, developed post-kala-azar dermal leishmaniasis (PKDL) In conclusion, PCR-based testing of lymph-node aspirates after treatment may be used as a prognostic marker for the future development of PKDL and may be useful in the follow-up of patients.