The Persisting Osler—V commemorates the fiftieth anniversary of the American Osler Society (AOS) and the centenary of the death of its namesake, Sir William Osler (1849–1919). Because of its anniversary significance, we chose to limit papers to those pertaining to Osler, his circle, his influence, and his ideas and opinions. Over the past half-century, the AOS has evolved to be more broadly concerned with medical history, medical biography, and the humanities as these relate to medicine than was the case at its inception. We predict that any future volumes of this series will contain a more diverse range of subject matter, since it has become increasingly difficult to say anything new or fresh about Osler. Few if any physicians have been studied so extensively with the obvious exception of St. Luke.