A study of the sand fly fauna was carried out in the endemic area ofAmerican cutaneous leishmaniasis (ACL) in the Municipality of Mesquita, State of Rio de Janeiro, in an area where dwellings (with humans and dogs infected by Leishmania (Viannia) braziliensis) have been recently visited by sloths. Weekly captures were made during two consecutive years in two different sites (1 m and 600 m above sea level) and in three different habitats in each site (domestic, extra-domestic and sylvatic) using CDC light traps and Shannon traps. The following species were identified: Brumptomyia (Brumptomyia) guimaraesi, B. (B.) nitzulescui, Lutzomyia (Lutzomyia) longipalpis, L. migonei, L. serrana, L. (Psathyromyia) lutziana, L. barrettoi, L. (Nyssomyia) intermedia, L. (N.) whitmani, L. (Mycropygomyia) schireiberi, L. quinquefer, L. sallesi, L. (Psychodopygus) ayrozai, L. pascalei, L. (Pintomyia) bianchigalatiae and L. lanei. The collection of B. guimaraesi and B. nitzulescui species indicates the proximity of the study area to the sylvatic habitat. Two important suspected vectors of ACL were found: L. intermedia and L. migonei. L. longipalpis, a proven vector of American visceral leishmaniasis (AVL), was also found in this area. L. intermedia, the predominant sand fly species, was collected by both methods of capture and in the three different sites. It was observed biting man inside houses, but it was less anthropophilic in the sylvatic habitat. Our observations suggest that altitude does not influence the dispersion of L. intermedia population in the Municipality of Mesquita. The data indicate that L. intermedia remains as a putative vector of Leishmania (V.) braziliensis in this locality. An hypothesis of a sylvatic transmission cycle in the area and its correlation with the domestic cycle are discussed in the present paper.