Our nation’s health care system continues to undergo significant transformation to address the quality and high cost of care. Accountable Care Organizations (ACOs) have become a substantial part of these efforts by realigning our current payment system to reward organizations that achieve high-value care. While the ACO concept continues to evolve, it can broadly be defined as: “a group of health care providers who accept shared accountability for the cost and quality of care delivered to a population of patients.” Physician-led provider organizations are quickly becoming one of the biggest drivers of accountable care activity. Typically, these groups are not hospital affiliated and instead include one or more independent primary care physician groups or practice associations that have a large combined patient population. The physician members of these ACOs lean heavily toward primary care, but are increasingly including specialists. Unlike hospital-led ACOs which may offer primary care, specialty care, and acute care to their patients, many physician-led ACOs are limited to providing primary care, yet maintain responsibility for the total cost of each patient’s care.