The 2014 Listening Project Report identified several research and data gaps related to Medicare. Among these was a need to better understand the inner workings of ACOs, including their internal payment structures and the specific tools they use to coordinate care and seek efficiencies. This roadmap focuses on these issues. A separate roadmap examines evidence about ACO’s impact on Medicare and the larger health care marketplace. Because ACOs — both within and outside of Medicare — are a relatively new form of health care payment and delivery, they are still being evaluated. Additional data, studies, and reviews will be forthcoming with time. However, some evidence relevant to the internal workings of ACOs does exist. AcademyHealth undertook this roadmap with the support of the Robert Wood Johnson Foundation.