This article is a historical-sociological account of the rise of physical diagnosis (auscultation and percussion) in 19th century medicine. It focuses on the spread of physical diagnosis, from the near exclusive confines of the hospital to the broader realm of medical practice. In particular, it sheds light on the relationship between diagnosis and treatment which turned out to play a most crucial role in the eventual success of physical diagnosis. On the one hand, critics argued that physical diagnosis lacked any practical value and that its introduction into medical practice would not contribute to the treatment of the patient. On the other hand, proponents of physical diagnosis maintained that medical treatment would benefit from better diagnostic knowledge and that the physician’s actions should be based on systematic diagnostic scrutiny. The article also sheds light on the negotiation between physicians and patients which took place during the introduction of physical diagnosis into private practice. In the last part of the article, it will be argued that the success of physical diagnosis was closely related to the co-production of a new form of professional expertise in 19th century medicine.