Authors Taylor Burke and Sara Rosenbaum examine the role of ACOs in the proposed legislation and conclude that they are in keeping with longstanding antitrust policies. The brief is the second in a series pertaining to antitrust law. The first, Health System Reform and Antitrust Law: The Antitrust Aspects of Health Information Sharing by Public and Private, discussed antitrust considerations that arise in health system transformation aimed at producing greater clinical integration and greater levels of information about the quality and cost of care.