The researchers used the National Survey of Accountable Care Organizations (NSACO), geographic data on Accountable Care Organization (ACO) locations, and publicly released performance data to assess the characteristics that drive quality and cost performance. They used a cross-sectional analysis of these existing, unique data sources to assess how organizational capabilities and market characteristics are associated with ACO performance. ACOs are a centerpiece of federal payment and delivery system reform efforts established in Medicare through the Affordable Care Act, but first-year performance and early evidence showed considerable variation across participating providers, with some achieving substantial savings and others achieving no savings. The goal of this study was to inform policymakers and providers of the ACO characteristics and capabilities associated with achieving savings and delivering high-quality care.