The work of the French philosopher Georges Canguilhem is inroduced here. Medical historiography is not the ultimate aim of Canguilhems work, but rather a tool for the analysis ef epistemological questions. These questions are to be investigated, as well as the art of medical history that Canguilhem consideres to be helpful for such investigations. French "epistemology", a direction of philosophy of science to which Cangilhem belongs, is discussed first. Canguilhem's epistemology does not aim at a rational reconstruction of decontextualized scientific results, but at an historical reconstruction of science. It analyses the functioning of scientific concepts in relation of their historical context. The main themes of Canguilhems work (biological normality, scientific ideology and history of physiology) are summarized in a second part of this study. Finally we investigate the importance of Canguilhem for modern research in history of medicine.