The Affordable Care Act (ACA) (full title: The Patient Protection and Affordable Care Act) (P.L. 111-148) will generate sweeping changes in the financing, organization, and accessibility of health and social services in the United States. The expansion of Medicaid and the establishment of state health insurance exchanges (HIEs) will vastly expand insurance access in the United States, with an estimated 30 million Americans gaining coverage (Banthin et al., 2012). The emphasis on integrated models of care, including patient-centered medical homes and accountable care organizations, introduces new opportunities to improve care coordination, reduce unnecessary service use, and make health care more cost-effective. Realizing these changes relies on the work of many health care professions. In this editorial, we make a case for how the social work profession can forge a leadership role in implementing this historic legislation. SOCIAL WORK EXPERTISE AND THE ACA Because the ACA is so bold and ambitious, it is important to consider how the unique skills and knowledge bases of social work and other health care professions align with its objectives and goals. An integrated approach is needed to maximize the ACA's potential to improve the health of the population. Four central qualities of the social work profession make it uniquely suited to advance a number of the objectives and goals of the ACA. First, social work situates individuals in the social contexts in which they live. Social workers understand that individuals are part of social networks, neighborhoods, and communities that influence their health choices and participation in health care. Understanding these social relationships provides us with insight into health behaviors and health outcomes that is necessary to achieve population health goals. Social workers likewise understand the relationship between health, education, employment, and other systems that form the nexus from which resources can be drawn to protect, maintain, and restore health. Social workers are familiar with the complex and overlapping systems that must be negotiated to ensure that the social, psychological, and economic needs of individuals and groups are addressed in a way that underscores optimal health. For instance, social workers know how to ensure that patients have what they need from multiple systems upon discharge, that discharge instructions are understood, and that resources are in place to ensure that those instructions can be followed. This knowledge is essential for avoiding unnecessary readmissions--events subject to financial penalties under the ACA. In a related sense, social work is guided by an evidence base that is informed by rigorous research within communities and collective wisdom gleaned from over a century of social work practice. Of importance is social workers' research to understand how mental health and physical health interact to enhance or impede functioning and patients' participation in health care treatment. Social workers devise plans based on knowledge of how the two interact and can help to ensure that the communication occurs that underlies optimal, sustained functioning and wellness. Evidence-based social work practice begins where individuals and groups are, in a way that is sensitive to cultural beliefs and health literacy. This orientation helps to ensure that recommendations for disease prevention and care management are understood and that patients and families are able to follow instructions when individuals become ill. It is important to consider one additional quality of social work, not because it is directed at those who will be covered by the ACA, but because it considers those who will not be covered. Approximately 29 million Americans will still lack health insurance after the ACA is fully instituted (Banthin et al., 2012). Social workers historically have targeted their services to such disenfranchised groups, including those who do not have a stable place in society, may lack housing and other basic services, and have no or irregular contact with the health system. …