Three new briefs from Families USA examine the details behind the idea of Accountable Care Organizations, or ACOs, new initiatives under the Affordable Care Act that, as described in the report, are “[entities] made up of health care providers that [agree] to be held accountable not just for lowering the cost of health care, but also for improving health care quality across the continuum of care, including acute care, post-acute care, long-term care, and behavioral and mental health care.” One brief reviews how ACOs will be paid by Medicare and how quality measurements should be selected. A second brief examines the incentive payment model behind ACOs, how initial expenditure benchmarks could be determined, and explains the minimum savings and loss rate determined by CMS. The third brief explores how beneficiaries could be assigned to an ACO and whether the assignment will be retrospective or prospective.