In this article a fragment of eight leaves in 4°, printed on the press of Thierry Martens and Johannes de Westfalia at Alost and part of a still undescribed edition of Boethius's Latin translation of Aristotle's Praedicamenta is discussed. With this discovery the known output of the first press in the southern Low Countries has risen to seven editions. The Praedicamenta were part of the so-called 'vetus logica', two editions of which were published by Conrad Braem at Louvain, the first undated, the second in 1475. The newly discovered fragment is closely related to the undated Louvain edition, and like it probably contained two further texts: Porphyrius's introduction to the Praedicamenta and Aristotle's De interpretatione. The complete edition would then have covered some sixty-two leaves in all. To date the fragment, the paper of all seven Alost editions was subjected to a new examina-tion (the previous ones having been carried out by Prof. Wytze Hellinga and K. Heireman S.J.), as was the manner in which the pinholes were applied to the paper. This investigation led to the conclusion that there were two presses operating simultaneously in the Alost printing shop. On the basis of this hypothesis it now seems possible that the newly discovered fragment was printed at the same time as the Petrus Hispanus which was completed on 26 May 1474, though the edition to which the fragment belongs, being shorter, would have been finished earlier. Finally there is a comparison of the texts of the Alost fragment and the work published by Braem at Louvain. From this it is possible to conclude, though without absolute certainty, that the Louvain text predates that of Alost. If this is indeed the case, it has interesting consequences for Braem's place in the history of printing at Louvain.