Locals in Filadelfia, the urban center of western Paraguay's Mennonite Colonies, see the public presence of indigenous Ayoreo `sex workers' as a moral stain on the city and a major social problem. These young women's practices upend local perceptions as well as established theoretical categories of sex work. They treat interactions with male `friends' not as `work' but as `play,' they do not see their practices as morally fraught; and they move in and out of the activity, until they leave it behind and marry within their own group. This dissertation, based on 49 months of long-term fieldwork, examines the cultural meanings of `sex work' among Ayoreo young women to understand how colliding ethical systems, framed by five decades of Ayoreo engagement with the market economy and intense Christianization shape the cultural production of gender and sexuality, and notions of exchange and the commoditization of bodies. Ayoreo `sex work' does not fit conventional academic models, which reduce such activity to proof of economic necessity or women's stigmatization of women. Rather than being a form of feminine submission or exploitation, it is a unique cultural phenomenon constructed in a web of social relations forged through processes of cultural change, religious hegemony, and economic shifts experienced by the Ayoreo over the twentieth century.