In the Amazon Basin, Trypanosoma cruzi infection is enzootic, involving a variety of wild mammals and at least 10 of the 16 reported silvatic triatomine bug species. Human cases of Chagas disease are increasing, indicating that the disease may be emerging as a wider public health problem in the region: 38 cases from 1969 to 1992, and 167 in the past eight years. This article reviews the status of Chagas disease in Amazonian Brazil, including known reservoirs and vectors, and the genetic diversity of T. cruzi. At least three subspecific groups of T. cruzi-T. cruzilZ1, T. cruziZ3 and T. cruziZ3/Z1 ASAT--are present. It appears that T. cruzil has an extant capacity for genetic exchange. Attention is also drawn to the risk of domestic endemicity, in addition to the tasks facing the disease control authorities.