Aristotle’s Topics, and especially, as far as the subject of this study is concerned, their central books (II-VII), played a role of central importance both in the medieval Latin and in the Arabic logical tradition. This did not occur without transformations, which affected the nature and the function of the loci of which these books set forth the theory. One of the most visible signposts of this tradition of re-elaboration of the Topics is represented by Themistius (ob. c. 388), to whom both Boethius and Averroes refer. Yet no work by Themistius on the Topics has come down to us in Greek. With a view to reconstructing the work(s) of this author, we have here collected and translated the passages that are attributed to him explicitly (with the exception of one of them) in Averroes’ Middle Commentary on the Topics, comparing them, where necessary, to the testimonies collected by Boethius in his De topicis differentiis. In addition – and this is a new element added to the file – we show that the Themistian classification of loci was taken up by Abū al-Barakāt al-Baġādī (ob. after 1164), author of a philosophical summa entitled al-Kitāb al-mu‘tabar (The meditated book). These three testimonies are all the more precious in that they are independent of one another. The study of the chapter in the logical part of al-Kitāb al-mu‘tabar, containing the Themistian classification of loci, of which a corrected text with translation is offered, shows that one finds in it some of the most singular aspects of this classification, as it appears in Boethius. Abū al-Barakāt al-Baġādī thus reveals himself to be closer than Averroes to the testimony of Boethius. This suggests the idea of a double redaction by Themistius of the classification of loci: one, more concentrated, comes from an introduction to the paraphrase of the central books of the Topics, which may have inspired Averroes; the other, more extensive, which will have been part of an original work, and inspired the classifications of Boethius and of Abū al-Barakāt al-Baġādī.