© Koninklijke Brill NV, Leiden, The Netherlands. Arnau de Vilanova, one of the most important physicians of the Latin Middle Ages, was familiar with the vast majority of Aristotle's works that had been translated into Latin. He used a wide range of them, such as the Organon - the introductory books on logic - and the natural philosophical books, which cover a different branches of knowledge. He used Aristotle as an authority, trying to reconcile him with the field of medicine as practiced in his time. In so going, he defined a new theoretical model of medicine by the standards of natural philosophy, while continuing to emphasize the boundaries between medicine and natural philosophy. This paper represents to a first attempt to investigate the Aristotelian quotations in the medical writings of Arnau de Vilanova.