 Alexander of Aegae wrote about the Categories (Simplicius, In Cat. 10.20; 13.16) and the De caelo (Simplicius, In DC 430.29–32). Since he is said to have been teacher of the Emperor Nero, his exegetical activity can be dated to the first half of the 1st century CE. Nothing can be said about the form of his literary production. This is also the case of two other interpreters of the Categories: Sotion and Achaius (Simplicius, In Cat. 159.23). Although their exegetical activity is much more difficult to date, there is one line of argument that places it in the 1st century CE. The information at our disposal is frustratingly meagre, but it is hard to escape the conclusion that the Categories continued to be at the centre of the exegetical activity on the philosophy of Aristotle. The situation did not change in the first half of the 2nd century CE. From Galen we learn that Adrastus of Aphrodisias and Aspasius wrote elementary commentaries on the Categories. From the way Galen refers to these commentaries, they must have been easily available and routinely used to introduce students to the Categories. Adrastus and Aspasius established themselves as respected interpreters of Aristotle. We know that their commentaries were still used about one hundred years later by the great Plotinus (Porphyry, Life of Plotinus. 14.12–14). Aspasius did not confine his exegetical activity to the Categories. He wrote commentaries on the De Interpretatione, the Physics, and the Metaphysics. These commentaries were used and quoted by later generations of commentators. The reputation that Aspasius enjoyed in antiquity explains why his commentary on Aristotle’s Ethics has survived. This commentary is the earliest surviving commentary on an Aristotelian text.