Ḥunayn ibn Isḥāq's Arabic translation of Galen's commentary on the Hippocratic Epidemics is an invaluable source for our knowledge of Galenic medicine and its transmission history, not least because much of it is extant only in Arabic. Its importance for the Arabic medical tradition is amply attested in the later medical literature. It also tells us much about the methods and self-image of contemporary translators. Throughout the translation, we find remarks by Ḥunayn discussing the quality of his source text, his own interpretation and also his attempts to reconstruct problematic or damaged passages. Based on an edition of these notes, their analysis and comparison to similar texts and Galen's own thought on editing and interpreting difficult medical texts, this article aims to situate Ḥunayn's methods in the context of the Greek-Arabic translation movement. It argues that his approach differs in important respects from that of preceding Greek-Arabic and Greek-Syriac translators and that he was indebted to Galen not just as a physician, but also as a translator and exegete.