The Ache, whose life history Hill and Hurtado recount, are a small, indigenous population of hunters and gatherers living in the neotropical rainforest of eastern Paraguay. Contact of Ache with outsiders, including other Indian groups, has been infrequent and hostile during the 400 years since the first arrival of the Spanish. The authors have gained their confidence over more than a decade in the field. Both in terms of access to Ache informants and in field data, their research is unique.