A polymerase chain reaction (PCR) technique for the diagnosis of canine leishmaniasis on bone marrow samples was developed which amplified a 120 bp DNA fragment of the Leishmania kinetoplast DNA, common to all Leishmania species. Forty-five of 46 dogs in which leishmaniasis had been diagnosed were positive with the PCR technique, whereas none of 41 healthy dogs gave a positive result. Fifteen dogs with leishmaniasis that had been treated for six months with N-methylglucamine antimoniate and allopurinol were also investigated. Seven were positive, implying that they remained infected despite the resolution of their clinical signs.