Triatoma brasiliensis is the most important Chagas disease vector in the drier regions of the "Brazilian Caatinga", colonizing both sylvatic and domestic environments, usually forming abundant colonies. Control trials using insecticides against domestic and peridomestic populations suggest that the T. brasiliensis has a high capacity to repopulate treated habitats from the neighboring sylvatic populations, making its elimination more complex. The aim of this work was to determine genetic variability among sylvatic, peridomestic and domestic populations of T. brasiliensis using head morphometry and random amplified polymorphic DNA (RAPD). Both morphometric analysis and RAPD patterns showed a separation between sylvatic and domestic populations, being the peridomestic ones between them. Based on this data, we suggest that there exists a flow between natural and artificial environments, being the peridomestic population mainly responsible for this interchange. It is possible that the peridomestic environment is maintaining the variability on the insects found on artificial habitats, which guarantee T. brasiliensis success on adaptation in both environments and also increase the risk of introduction of new Trypanosoma cruzi strains in the domestic cycle of Chagas disease in this region.