As more health care providers join together as accountable care organizations (ACOs)—there were 428 ACOs as of last January—it's important to understand the capabilities needed to be successful under this care delivery model, in which providers take on responsibility for the total costs and quality of care for a designated group of patients. A new blog post from analysts at the Premier Research Institute reports on the implementation strategies, challenges, and lessons learned from four early adopters of accountable care.