The passage of the Affordable Care Act saw the creation of Accountable Care Organizations (ACOs), a new approach to healthcare delivery moving from fee-for-service toward population health. This paper presents a case study of the Memorial Hermann ACO (MHACO), launched in response to the Medicare Shared Savings Program, with goals to align physician and hospital incentives, practice evidence-based medicine, develop care coordination, and increase efficiency. Building blocks included an affiliated primary care network, a clinical integration program (involving shared electronic medical record platforms and quality data reporting), and significant investments in information technology. Presented is the approach taken to form MHACO; the management structure, technology developed, and a 2-year experience. Incorporated in July 2012, the MHACO involved 22 000 Medicare patients. In 2015, Centers for Medicare and Medicaid Services released data showing a composite quality score between 80 and 85 (from a maximum 100) and nearly $53 million in total savings (or 11% of expected expenditure), making MHACO one of the most successful nationally.1 In fewer than 5 years, almost 500 ACOs have developed, and by some estimates, a quarter of Medicare patients are currently enrolled in an ACO. Although ACOs to date have focused on primary care, the future will increasingly involve specialists. At Memorial Hermann, neurosurgeons took an early role in forming collaborative partnerships with the hospital, and started programs that served as precursors to the ACO model. This paper ends with an overview of ACO development, likely changes going forward, and a discussion of the role of specialists in general, and of neurosurgeons in particular.