By using a PCR assay specific for Leishmania braziliensis in blood samples, we detected this parasite in patients cured by immunotherapy or at different stages of treatment. We also found the parasite in subjects who had never suffered leishmaniasis but who had lived in endemic areas and migrated to nonendemic ones many years ago. These results suggest that L. braziliensis infections are difficult to eradicate and that a clinical cure but rarely a complete elimination of the parasite is generally accomplished.