observations made in the field and in the laboratory on three vectors of trypanosoma cruzi: triatoma barberi, t. pallidipennis and t. dimidiata are here presented. results are compared in relation with their ecotopes, vectorial capacity, biological characteristic, entomological indexes and capture places. in relation with their ecotopos t. barberi has preference for the interior of the human home, in walls, directly in contact with beds; t. pallidipennis, when it is inside the houses, prefers floors and among clothes, although their main ecotope is wild; t. dimidiata has localization in floors, specially under the beds, in the angle between wall and floor; t. barberi and t. dimidiata are attracted by the light. the cycles of life were of 523, 171 and 510 days, respectively for triatoma barberi, t. pallidipennis and t. dimidiata. the vectorial capacity was determined according to the time taken in defecating during or after its sucking blood: t. barberi defecates during its feeding, while t. pallidipennis and t. dimidiata make it from 10 to 20 and of 20 to 30 minutes after starting the process, respectively. the indexes of natural infection were of 56.6 for t.barberi, 29 for t.pallidipennis and 15.6 for t. dimidiata, the metacyclogenics indexes that indicate percentages of metacyclics trypomastigotes in later intestine of vectors was in t. barberi 76.6, t. pallidipennis 15 and t. dimidiata 26, with what it can be concluded that the first species is the best transmitter of t. cruzi in mexico.