Avicenna’s al-Qānūn fī al-Ṭibb provided the foundation for the teaching and practice of medicine in post-1200 Islamic societies. Its abridgments and commentaries were used to train physicians well into the nineteenth century. However, these commentaries and abridgments have barely received the attention they deserve by historians who often dismiss them as being derivative and unoriginal. In this paper, I shall show that not only do the commentaries contain much that is original or at least worthy of attention, but that closer examinations of these texts can reveal much about medical education and the processes by which these commentaries were generated. The most popular abridgment of the Qānūn was the Mūjaz which is attributed to Ibn al-Nafīs (d. 1288). Although many commentaries were composed on it over the years, one of the most popular ones was Kitāb al-Nafīsī by Nafīs ibn ‘Iwaḍ al-Kirmānī (d. 1449), produced under the patronage of Ulugh Begh in Samarqand. Kitāb al-Nafīsī drew upon the earlier commentary by Jamāl al-Dīn al-Aqsarā’ī (d. 1337), and formed the basis of a later commentary by Ibn al-Mubārak al-Qazwīnī (d. 1521), a physician at the courts of three successive Ottoman sultans Bayezid II, Selim I and Süleyman. These three texts thus formed a network of commentaries that were copied, read and taught across Egypt, Syria, Anatolia, Iran and Central Asia over the course of two centuries. The paper will examine some manuscripts of these works to gain insight into the movements of these texts, and their use in medical education. It will also examine some passages from the medical commentaries themselves to reveal the nature of the discussions, and how the commentators moved the discussions beyond the source text into uncharted territories. In some cases, this resulted in very novel consequences for medical theory.