Advances in the prevention, early detection, and treatment of cancer have resulted in an almost 14% decrease in the death rates from all cancers combined from 1991 to 2004 in the overall US population, with remarkable declines in mortality for the top 3 causes of cancer death in men (lung, colorectal, and prostate cancer) and 2 of the top 3 cancers in women (breast and colorectal cancer). However, not all segments of the population have benefited equally from this progress, and evidence suggests that some of these differences are related to lack of access to health care. Lack of adequate health insurance appears to be a critical barrier to receipt of appropriate health care services. This article provides an overview of systems of health insurance in the United States, demographic and socioeconomic characteristics associated with health insurance coverage, and economic burdens related to health care among individuals and families. This article also presents data on the association between health insurance status and screening, stage at diagnosis, and survival for breast and colorectal cancer based on analyses of the National Health Interview Survey and the National Cancer Data Base. Although this article focuses on associations between health insurance and cancer care utilization and outcomes, it is important to recognize that barriers to receipt of optimal cancer care are complex and involve patient-level, provider, and health system factors. Evidence presented in this paper suggests that addressing insurance and cost-related barriers to care is a critical component of efforts to ensure that all Americans are able to share in the progress that can be achieved by access to high-quality cancer prevention, early detection, and treatment services.