Two Aotus trivirgatus (owl monkeys) were infected experimentally with Leishmania braziliensis and two with L. mexicana strains of Panamanian origin in a pilot study to determine the susceptibility and the course of infection of cutaneous leishmaniasis in this primate species. Montenegro skin tests performed on all animals prior to parasite inoculation were negative. A standardized inoculum of promastigotes was injected intradermally on the nose of each monkey. All of the animals developed infections which lasted from 3.5 to 8.5 months. Depigmentation developed at the site of the inoculation in all of the subjects. The severity of the resulting lesions was greater in the animals infected with L. braziliensis. Positive skin tests developed in three A. trivirgatus at days 62, 76, and 139 postinoculation, respectively. An explanation for the negative skin test in the fourth animal is discussed.