The diagnosis of visceral leishmaniasis (VL) remains problematic for physicians in Syria, because the appearance of this disease is new and its clinical criteria are similar to Malaria, Tuberculosis, and Toxoplasmosis symptoms. For this reason, we used the specific antigen (rK39) of Leishmania donovani complex, in order to certify the appearance of visceral leishmaniasis in some patients. Then we followed the infected cases with VL during treatment (15 days) and after treatment (10 days) with Glucantime®. We noted an improvement in clinical criteria and a significant decrease in the parasite numbers as well as in the specific L. donovani antibodies.