A morphometric survey examined adult specimens of Lutzomyia whitmani (Antunes & Coutinho) captured at 5 municipalities in southeastern and northeastern Brazil to compare the populations. The localities were Ilhéus (Bahia), Martinho Campos (Minas Gerais), Corte de Pedra (Bahia), Baturité (Ceará), and Amaraji (Pernambuco): all are known foci of American cutaneous leishmaniasis. Fifteen males and 15 females from each population were analyzed morphometrically for 42 and 37 characters, respectively. Statistical data alone were insufficient to discriminate among the 5 populations. Further analysis generated phenograms that indicated there were 2 spatial clusters: the 1st was composed of specimens from Ilhéus (Bahia) and Baturité (Ceará) and the 2nd of specimens from Martinho Campos (Minas Gerais), Corte de Pedra (Bahia), and Amaraji (Pernambuco). Although insufficient to define the taxonomic status of the populations studied, the results delineated the existence of biogeographical structuring within L. whitmani. Complementary studies on the susceptibility to Leishmania braziliensis infection in the 5 populations are in progress to clarify the relationship between the 2 biogeographical clusters and American cutaneous leishmaniasis transmission in those Brazilian regions.