 As the list of his work shows, Alexander was a prolific writer. His writings comprise both commentaries (hupomnêmata) on the works of Aristotle and several systematic treatises of his own (including works on ‘problems’, consisting of series of essays on different Aristotelian texts and topics). Of the commentaries, the following are extant:  On Prior Analytics I, Topics, Metaphysics, Meteorologica, and On Sense Perception. Of the commentary on the Metaphysics only the first five books are by general consent accepted as genuine; the remaining nine books are attributed to the late commentator Michael of Ephesus (11th-12th century CE.). The commentary on the Sophistical Refutations, ascribed to Alexander in some manuscripts, is considered spurious. References by later commentators show that Alexander’s commentaries covered all of Aristotle’s theoretical philosophy, including his physical writings (with the exception of the biological works). The list of his lost work is long: there are references to commentaries on the Categories, De interpretatione, Posterior Analytics, Physics, and On the Heavens, as well as On the Soul and On Memory. Alexander did not write commentaries on Aristotle’s Ethics or Politics, nor on the Poetics or the Rhetoric. That he had quite some interest in ethical problems, however, is witnessed by the discussions in his own treatises. Among the extant short systematic writings the following are regarded as genuine: Problems and Solutions, Ethical Problems, On Fate, On Mixture and Increase, On the Soul and a Supplement to On the Soul (‘Mantissa’ lit. ‘make-weight’) that not only contain discussions of questions concerning psychology but also problems in physics, ethics, vision and light, as well as fate and providence. The ‘Mantissa’ may not be by Alexander but a compilation of notes by his students. The rest, Medical Questions, Physical Problems, and On Fevers are considered spurious. Of his lost works some have been preserved in Arabic because they were highly influential (see D’Ancona &amp; Serra 2002): On the Principles of the Universe, On Providence, Against Galen on Motion, and On Specific Differences. Because of Alexander’s prestige and authority as an interpreter of Aristotle, many of his works now lost were incorporated in the commentaries of his successors, whether they name him or not. Nothing certain is known about the relative chronology of his writings, but this is not an issue of much importance, since his commentaries may well represent the results of many years of teaching, with later insertions and additions, in a way quite similar to Aristotle’s own texts. This would explain the lack of any attempt at elegance and the occurrence of inconsistencies or unclear transitions in Alexander.