Professionalism may not be sufficient to drive the profound and far-reaching changes needed in the US health care system, but without it, the health care enterprise is lost. Formal statements defining professionalism have been abstract and principle based, without a clear description of what professional behaviors look like in practice. This article proposes a behavioral and systems view of professionalism that provides a practical approach for physicians and the organizations in which they work. A more behaviorally oriented definition makes the pursuit of professionalism in daily practice more accessible and attainable. Professionalism needs to evolve from being conceptualized as an innate character trait or virtue to sophisticated competencies that can and must be taught and refined over a lifetime of practice. Furthermore, professional behaviors are profoundly influenced by the organizational and environmental context of contemporary medical practice, and these external forces need to be harnessed to support--not inhibit--professionalism in practice. This perspective on professionalism provides an opportunity to improve the delivery of health care through education and system-level reform.