Having formerly had some acquaintance with American leishmaniasis in Paraguay, and believing that the solution of the transmission problem of the leishmania' infections might be more readily accomplished in the forests of South America than elsewhere, the writer returned to Paraguay in 1930, with the intention of carrying out epidemiological investigations on this subject. For the purpose of acquiring clinical knowledge he lived in a village where sufferers from this malady tended to congregate, proposing, thereafter, to take up residence in an endemic area in order to examine the possible connection between the forest flora and fauna and the occurrence of leishmaniasis in the local human inhabitants. A preliminary clinical study of about a hundred cases having been made, he was about to embark upon a period of field research when the world -wide commercial depression reached South America. Further investigations were, thereby, rendered financially impossible and the chief part of the work had to be abandoned. Nevertheless, as American leishmaniasis has received but slight attention in English scientific literature, the writer feels justification in contributing this paper on the modern views of the disease, incorporating therein such original observations as he has had the opportunity of making.