Studies were carried out on the role of rodents, marsupials and triatoma bugs in the wild cycle of Trypanosoma cruzi. The area studied, located in the county of formosa, State of Goiás, Brasil, belongs to the "Província do Cerrado". The following animals were collected and examined: 963 rodents, 11 marsupials and 766 wild triatomid bugs. The infection rates for T. cruzi were as follow: 36.3% for the marsupials, 0.1% for the rodents, while all the triatomids were negative. The role of the collected mammals in the maintenance and circulation of T. cruzi in the wild environment is discussed. In addition, some epidemiological aspects of the domestic environment were also studied.