Applying standards of virtue that define the "good doctor" in a complex and technologically sophisticated health care system is often challenging and sometimes confusing. What are the characteristics of a "good doctor," who wishes to live up to high ethical and professional standards but who also must live and work in a health care system in which moral ambiguity is pervasive? Medical educators are urgently faced with such questions as their schools try to equip students with the skills and capacities required of the virtuous physician. The author describes how Aristotelian concepts of virtue can be used to guide medical educators in defining and teaching virtue. He then discusses how such traits as the ability to tolerate moral differences and ambiguity, the ability to develop thoughtful individual moral positions, and the capacity to respect and understand various cultural traditions may be what might be considered virtues in today's health care system. A "good" doctor, then, would be someone who is thoughtful, fair-minded, respectful of differences, and committed to his or her professional values.