Accountable care organizations: a primer.

Accountable care organizations (ACOs) are being hailed as a promising element of health care reform, as some believe they will be critical to improving the quality of care and holding down costs. Several state and federal ACO demonstration projects are scheduled to begin in the near future. Yet, questions abound as to what exactly an ACO is and how they work. This article describes the concept, outlines challenges to implementing ACOs, and discusses concerns about this new care delivery and payment model.