Almost 40 years after Hiatt1 called on physicians to become stewards of the scarce resources devoted to health care, physicians have taken on key leadership roles at multiple levels. The Choosing Wisely Campaign is a physician-led initiative that focuses on individual physician decision making as an opportunity to improve care and lower costs by avoiding unnecessary and often harmful treatments.2 Physicians are also taking on prominent leadership roles in new health care delivery and payment models, most notably accountable care organizations (ACOs), that encourage and reward achievement of better outcomes while managing the total costs of care.3