The engagement of German biomedicine in the design and execution of Nazi programs of "racial cleansing" was extensive and was organized by physicians and other professional leaders. In its active involvement and acquiescence, the German medical profession, one of the most sophisticated and respected medical enterprises in the world, dishonored itself and raised profound and persisting questions about the nature, strength, and relevance of the medical ethos and the relationship between medicine and the policies and programs of the state. Efforts to examine the history of German medicine under National Socialism are increasing in scale and number and involve German scholars to an important and expanding extent. Today, many bioethical issues, based on an increasingly sophisticated science and technology, confront medicine. A major lesson from the Nazi era is the fundamental ethical basis of medicine and the importance of an informed, concerned, and engaged profession.