In the United States, concern about breast cancer has generated policies and programs aimed at increasing screening mammography and treatment access for the uninsured and underinsured. Oriented toward the importance of early detection and the state's responsibility to ensure health care access to its citizens, these policies and programs reflect and reinforce a moral economy of disease management that shapes the ethical behavior of patients, providers, and advocates. In contrast, the moral economy of market-based health care generates norms and assumptions about individual responsibility for health and limits expectations of the state in providing access to health care. Using breast cancer care for structurally vulnerable women as a focal point, this dissertation examines the social effects of intersecting moral economies of breast cancer management and market-based health care. It describes the relationships between public policies, social and economic marginalization, and gaps in health care access. Based on 18 months of ethnographic field work in Southern Arizona, I report findings from interviews with physicians, nurses, advocates, clinic office staff, and community health workers; from recurring discussions with women undergoing treatment for breast cancer; and from participant-observation in cancer-focused events and activities. This dissertation explores how policies that extend low-cost or free health care to broad populations also reproduce social exclusion and complicate what it means to be uninsured in America. I describe how everyday practices of health care, including determinations of eligibility for public insurance, reflect and reinforce social inequities based on citizenship status, gender, and occupational status. I conclude that the organization of cancer care for structurally vulnerable women effectively directs the focus away from the state's responsibility to provide health care access and instead privatizes that responsibility so that it resides with structurally vulnerable clinics and non-licensed health care staff. Furthermore, a charity approach to managing cancer care for unauthorized U.S. residents diverts public responsibility for their social exclusion to private entities. Finally, the findings of this dissertation contribute to debates about health reform efforts, such as the Affordable Care Act, by outlining the relationship between moral worth and government entitlements.