7-[5'-(3'-phenylisoxazolino)methyl]-8-hydroxyquinoline a new synthetic 8-hydroxyquinoline derivative, was found, for the first time, to inhibit the multiplication in vitro of Leishmania tropica, Leishmania major and Leishmania infantum at micromolar concentrations. For each test we calculated a 50% inhibitory concentration (IC50) and the IC50 values found after 48 h are: 0.4 microgram/ml for L. tropica, 0.88 microgram/ml for L. major and 0.62 microgram/ml for L. infantum. As positive control, amphotericin B, a standard antileishmanial drug was used.