The clinical characteristics of acute and chronic Chagas' disease in central Brazil are described (29 acute cases and 111 chronic cases). The geographical distribution of Trypanosoma cruzi zymodemes in this region was mapped. Zymodeme (Z) 1 was identified in 12 acute cases, Z2 in 13 and repeated xenodiagnosis gave the same zymodeme identification. The clinical pictures of the Z1 and Z2 acute phases were similar. Resistance to benznidazole treatment occurred after either Z1 or Z2 acute infections. Only 14 positive xenodiagnosis were obtained from the 111 chronic phase patients examined. For 12 of these 14 patients the zymodeme was identified. All 12 carried Z2, 10 of whom had mega involvement. There were several possible explanations for the failure to detect T. cruzi Z1 in chronic Chagas' disease with mega syndromes: suggestions were made for follow-up investigations.