The Commentary on the Categories by Abu l-Farag ibn at-Tayyib is an important representative of the Aristotelian tradition in Arabic culture. Formally based on late antique commentaries on Aristotle's Categories, it provides the last example of the learned tradition still alive in eleventh-century Baghdad. The introduction offers a general survey of the commentaries on Aristotelian Categories , from the first Greek texts to the Arabic version featured here. The life and works of Ibn at-Tayyib are also discussed. Systematic comparison with surviving Greek commentaries and a series of thematic studies elucidate the author's method. The critical edition of ibn at-Tayyib's Commentary is accompanied by a detailed summary, which facilitates its use by readers unfamiliar with the Arabic language.