Al-Rāzī (m. 925) is known as one of the most prominant physician of the Arabo-Islamic Middle-Ages. Although he believed experience played a central part in the building of medical knowledge, he also defended the need for moder physicians to appropriate the legacy of the Ancients. This paper will examine al-Rāzī's dynamic relation to the Greek sources, especially Galen. It will address two main questions. First, why did al-Rāzī consider the transmission of Greek knowledge as essential, especially when it comes to epistemological debates? Second, how did he relate to this knowledge? Three texts, each one bearing a very different nature, will come under scrutiny: The Comprehensive Book of Medicine, the Doubts on Galen, and finally the al-Rāzī 's abridgement of Galen's Method of Treatment. I will try to show that for this author, the Greek medical tradition is a call for expansion and correction.