This innovative ethnographic study animates the racial politics that underlie genomic research into type 2 diabetes, one of the most widespread chronic diseases and one that affects ethnic groups disproportionately. Michael J. Montoya follows blood donations from “Mexican-American” donors to laboratories that are searching out genetic contributions to diabetes. His analysis lays bare the politics and ethics of the research process, addressing the implicit contradiction of undertaking genetic research that reinscribes race’s importance even as it is being demonstrated to have little scientific validity. In placing DNA sampling, processing, data set sharing, and carefully crafted science into a broader social context, Making the Mexican Diabetic underscores the implications of geneticizing disease while illuminating the significance of type 2 diabetes research in American life.