Needle sharing by intravenous drug users (IVDUs) has been proposed as providing an alternative, artificial, and anthroponotic cycle for leishmania transmission. We looked for parasites in syringes discarded by IVDUs using two different PCR techniques. Leishmania spp were detected in 65 (52%) of 125 syringes collected in southern Madrid, Spain, in 1998, and in 52 (34%) of 154 collected in southwestern Madrid in 2000-01. We found shared restriction fragment length polymorphisms in 12 of 65 positive samples tested, suggesting that syringe sharing can indeed promote the spread of leishmania clones among IVDUs.