Searching for one word to describe the state of mind of the physician in the United States today, we might choose beleaguered. Threats appear from all sides--from payers, would-be managers of care, the growth of technology, and even patients. The rhetoric is one of siege and battle, and the dynamic seems to be a clash of values from which only one winner can emerge. But scientific and health services research suggest otherwise. Science suggests that health care could, indeed, perform a great deal better than it does today and that a shared aim of improving health outcomes for patients at a cost that society can afford is sensible and within reach. However, achievement of these improvements will require of physicians not handwringing and resistance to change but concerted, positive, capable leadership. The goal of this series in Annals is to describe a new knowledge base that will help physicians participate effectively in the redesign of the health care system. The series is intended to raise the curiosity of physicians about the skills they will need to become more active and influential citizens of the health care community in accomplishing improvements. These skills will help physicians better deploy their clinical expertise and professional purpose in a debate that has heretofore been informed primarily by economics.