A total of 1,197 wild animals from Pará State north Brazil, were examined for haematozoa. Trypanosoma cruzi-like parasites were found in 13 different species, and were particularly common in a variety of marsupials (Didelphidae), porcupines (Coendou spp.), armadillos (Dasypus novemcinctus) and coatimundis(Nasua nasua). Three human infections are reported, making a total of seven autochthonous cases of Chagas's disease from Pará since the first were described in 1969. A serological survey of 5,319 inhabitants from the Belém suburbs revealed 14 positive reactions with immunofluorescent antibody titres greater than 1:64, and 15 equivocal reactions at 1:16. No evidence was found of silvatic species of triatomine bugs (Hemiptera: Reduviidae) colonizing houses, but occasional infected specimens of Panstrongylus geniculatus and Rhodnius pictipes were found in suburban houses, near the forest. Human infection is considered to be silvatic in origin. Chagas's disease could become endemic in the Amazon Basin if silvatic triatomine bugs were able to adapt to a domestic habitat: the real danger, however, is in the possible importation of already domiciliated vector-species along the newly opened highways, from other endemic regions of Brazil. Other Trypanosoma species were recorded in a variety of wild animals. Haemogregarines were found in some marsupials and rodents, and piroplasms in marsupials and a single armadillo.