Adult patients with mucosal leishmaniasis (ML) were enrolled in a randomized, double-blind, placebo-controlled, dose-escalating clinical trial and were randomly assigned to receive three injections of either the LEISH-F1+MPL-SE vaccine (consisting of 5, 10, or 20 μg recombinant Leishmania polyprotein LEISH-F1 antigen+25 μg MPL(®)-SE adjuvant) (n=36) or saline placebo (n=12). The study injections were given subcutaneously on Days 0, 28, and 56, and the patients were followed through Day 336 for safety, immunological, and clinical evolution endpoints. All patients received standard chemotherapy with sodium stibogluconate starting on Day 0. The vaccine was safe and well tolerated, and induced both humoral and cell-mediated immune responses. Furthermore, intracellular cytokine staining showed an increase in the proportion of memory LEISH-F1-specific IL-2(+) CD4 T-cells after vaccination, which was associated with clinical cure. This clinical trial shows that the LEISH-F1+MPL-SE vaccine is safe and immunogenic in patients with ML.