A little more than two years ago, Premier, a national performance improvement alliance of U.S. hospitals and other health care sites, launched a large-scale collaborative to develop an effective accountable care model that could be replicated across hospitals, health systems, and physician practices. In a new Commonwealth Fund report, Premier leaders provide an overview of strategies for implementing accountable care organizations (ACOs) that effectively balance cost control with efforts to improve health outcomes and enhance satisfaction with care. Readers will find a model for a successful ACO, payment options and performance metrics, examples of ACOs in action, early challenges faced, and policy recommendations that would support formation of these organizations across the nation.