Physicians hold numerous types of leadership positions in academic, executive, and/or clinical environments. To be successful, physician leaders must exert power, or social influence, as power is conceptualized in social psychology. The power of leaders accrues through their positions, expertise, or other factors, such as communication abilities or their ability to influence others to identify with the vision they espouse. This article discusses the types of leadership roles that physicians play and the power types they must apply in these roles. Crossing all leadership roles are a series of necessary personal characteristics and interpersonal competencies that result in what has been called "referent power," a more subtle form of social influence that is crucial for success regardless of position. Leadership training that includes practice in cultivating these personal characteristics and interpersonal competencies should be an essential component of medical and graduate medical education. Studying the types and nature of power also would be a valuable contribution to courses on professionalism in medical practice. Examples are provided of the types and uses of power that may be applied in the various leadership roles that physicians hold.