Of 151 Trypanosoma cruzi stocks from 117 different individual hosts collected in the states of Amazonas and Rondonia, 147 from 113 hosts were identified as zymodeme 1 (Z1). These included T. cruzi stocks from three marsupial species, two rodent species and three triatomine species although most were from the common opossum, Didelphis marsupialis. One T. cruzi stock from Rhodnius robustus was identified as Z1 with a Z3 PGM character, one from Sciurus sp. as Z3 and two from Monodelphis brevicaudata and Panstrongylus geniculatus as Z3 with a Z1 ASAT character. The ways in which stocks were isolated and grown up in vitro did not influence isozyme profile. These results support earlier evidence from Pará State that Z2 is absent from the Amazon basin and that the distribution of T. cruzi zymodemes in this region is quite different to that in endemic areas on the south of the continent.