We have a lifelong relationship with our health. We depend on others to help finance our health risks through insurance, doctors to advise and treat us, drug companies to create treatments, and hospitals to house and care for us when we are in our worst health. Accountability is both an individual and a shared responsibility. Many physicians, nurses, other clinicians, and even employees of health care organizations feel a sense of responsibility when a patient’s health deteriorates. Was something missed? Could we have reached out more effectively? Could we have known something sooner? Would a stronger relationship with the person have made a difference? This professional accountability has always been at the heart of health care as a profession. Starting in 2006, a refined concept of tying this professional accountability to financial accountability emerged: the accountable care organization (ACO). Since the 2012 launch of the Medicare Shared Savings Program (MSSP), the flagship ACO program, concepts have turned into operations and spread widely. Yet Medicare, both traditional and Medicare Advantage, has continued to draw most of the attention and has nearly twice as much participation in ACOs.