We studied the efficacy of WR279396, a topical formulation of aminoglycosides that cures 100% of cutaneous leishmaniasis lesions in mice. We conducted what is to our knowledge the first controlled study of WR279396 therapy for clinical cutaneous leishmaniasis. A total of 45 Colombian soldiers, all men, were randomly assigned to treatment with WR279396 (33 patients) or placebo (12 patients). Each lesion was treated twice daily for 20 days. Lesions were measured at the end of therapy and at 45, 90, and 180 days after treatment began. A total of 17 (61%) of 28 assessable WR279396-treated patients were cured, and 5 (55%) of 9 assessable placebo-treated patients were cured (P = 0.9). For the 36 lesions treated with WR279396 that were cured, cure took a mean of 35 days, whereas for the 6 lesions that were cured in the group of patients receiving placebo, cure time took a mean of 56 days (P = 0.04). WR279396 is a nontoxic topical formulation that significantly accelerated cure time in patients with Leishmania panamensis cutaneous leishmaniasis.