Using vegetation and morphoclimactic domain maps the areas of dispersion of Lutzomyia intermedia were studied and the following conclusions were obtained: 1 - L. intermedia is a sandfly of the forests which have their maximum growth at the humid slopes although these forests can also be found in plains and areas with low hills. 2 - In Brazil these slopes are found at the Serras do Mar and Mantiqueira and in Argentina ath the Andes Mountains in the northwest of the country. 3 - This species probably occurs also in the forested mountainous areas of the northeastern region of Brazil.