In the last two years, we have been working on a Graeco-Arabic edition of Book IX of Galen’s On Simple Drugs, which also takes into account an abridged Syriac version. The starting point was a non-negotiable complete recension of all the manuscript witnesses. Our aim is to look for the point of contact between the Greek and the Arabic traditions, understanding the complex process that brought about the translation, and from there to reach the most ancient stage of the Galenic tradition that it is possible to attain. This approach opens new dimensions for stemmatological and editorial discussion that deserve to be cautiously explored.