Presumptive and confirmative techniques for searching mammals which could be reservoirs for Leishmania parasites from man are described. The changes of immobilising and agglutinating titers for promastigotes from culture by sera from normal and exposed mammals after single or repeated intradermal inoculation of promastigotes are described. A fall in titers of agglunation is observed in sera from hamsters, Holochilus venezuelae and Didelphis marsupialis after inoculation with L. mexicana mexicana from Panama and L. garnhami from the Venezuelan Andes region. The nature of this phenomenon is discussed. Xenodiagnoses were made with Lutzomyia townsendi on Holochilus venezuelae and Sigmodon hispidus experimentally infected with L. mexicana mexicana, L. mexicana amazonensis, L. braziliensis and L. garnhami. The tests were read by means of microscope examination of stained faeces excreted by sandflies between 108 to 132 hours after feeding on infected animals. Positive results were obtained in 23% of experiments using mammals with localized lesions, allowing sandflies to feed freely on anesthetized animals with one to several localized lesions.