The 2016 performance year Accountable Care Organization (ACO) report is based on the Centers for Medicare and Medicaid Services (CMS) released data. It includes both financial and operational results for all 432 ACOs active during the year. ACOs are authorized under the Medicare Shared Savings Program (MSSP) as part of the Patient Protection and Affordable Care Act (PPACA or ACA). This work is divided into two main sections, listings of ACOs-alphabetically, by state, and by county, along with quality results-as well as single-page ACO report cards for each entity. Additionally, a data dictionary with CMS definitions and data collection information in included in Appendix A. Each ACO report card includes a summary header with ACO name and ID as well as key information such as number of assigned beneficiaries, track type, benchmarks, and savings (total, minimum/target, and earned amount). Another section provides beneficiary breakdowns by population type (ESRD, disabled, dual eligible, and non-dual eligible) and demographic factor (age, race, and risk score) as well as trends across three baseline years plus the current performance year. The report card's Provider Summary section identifies the number of participating providers by type, and the Market Coverage section lists the top counties, ranked by number of beneficiaries, served by that ACO. The Utilization and Cost Metrics area provides per-capita annual spend and number of events (discharges, visits, or services) by service type. Symbols indicate the lowest and highest quartile performers across the national population for fast visual identification of potential outliers.