The people of Pichataro, a Tarascan Indian village in the highlands of west-central Mexico, use Western medicine as well as native curing specialists and folk treatment practices. In this study, the authors examine why residents choose one type of health care over another, setting the analysis within the broader context of the Pichatara medical system. Villagers generally are poor and have limited access to sources of Western health care. They use their medical knowledge--which the authors describe in depth--to evaluate the meaning, severity, and potential consequences of an illness. When an illness is considered grave, alternatives are ordered on the basis of probability of cure, so a physician is generally preferred; when an illness is not considered life threatening, alternatives are ordered on the basis of cost, so self-help or use of a local curer is most likely. These preferences have resulted in the development of a comprehensive set of "rules" for making decisions about treatment. The authors' firsthand experience with the community and their understanding of the role of illness in the lives and thoughts of its residents form the substance of this well-known work.