A prospective activity on Chagas' disease is reported in a wide region of colonization projects at the northern part of Minas Gerais. Triatomine-trypanosome search and sorological clinical inquiry among the population revealed a marked presence of triatoms in the area, with more than 60% of the dwellings infested by T. infestans or T. sordida, with global indexes of positiveness to T. (S.) cruzi at the level of 6.0% of the captured bugs. Two distinct situations are defined according to the dwelling place of these species, T. infestans being undoubtedly associated to the precarious patterns of the poorer population's dwellings, especially in Lagedinho and Gado Bravo, with high indexes of domicile density of this species. T. sordida apparently prevails on the southern part of Janaúba, and we may suggest that the species is still in the predominant wild phase, with sporadic domiciliated foci. The analysis of the population reveals relative high indexes of infection (about 10%), sorologically demonstrated, showing recent transmission through positive examinations in low-aged persons. The apparent scarcity of serious clinical forms suggests at first that Chagas' disease is, at the moment, being implanted as a human disease and is reproducing there, which must have occurred in a large extension of the nation, for the past two hundred years. Parallel to the ecological study of the interaction man-vector-trypanosome, the detected situation seems to constitute an important model for concrete and actual situations, as the conquest of Amazonia inclusive and specially in relation to the measures taken regarding the convenient prevention in benefit of the pioneer populations.