Sir William Osler was an outstanding figure in American and British Medicine during the early years of this century. Over fifty years after his death, his name is still remembered and honored, whereas other leaders who were equally important in the eyes of their contemporaries have been relegated to the realm of history. This brief review attempts to discover what special qualities have kept Osler's memory vivid. No single characteristic of his skill, science, or personality seems in itself to explain his continuing reputation. Rather, a combination of his eminence in several different medical schools, his presence at a time of revolution in medical teaching and thought, his authorship of one of the most successful medical textbooks, and an enthusiastic claque of ex-students and colleagues seem to have combined to maintain his memory as a leader of medicine.