Summary — Tire works of John of Wales, the English minorite who died ca. 1285, enjoyed well-deserved renown up to the XVIth century, although they are unjustly forgotten today. They comprised several areas: predicatory, politico-moral, philosophical, comentarist (N.T.), polemical-catechistic, and canonical. His influence in the Iberian peninsula has been recognized, but insufficiently analyzed. A tipical case is Catalonia. The existence of John of Wales' works in that region is numerous: 29 manuscripts in Latin, 9 translations into Catalonian, and at least 5 incunabula. Information proving the presence and utilization of his works during the last two centuries of the middle ages is abundant, and it justifies the profound influence his works exerted. The Catalonian-Aragonese kings strived to obtain copies of the Communi-loquium for their royal addresses to parliament. Church dignitaries as well as noblemen resorted to this work to embellish their replies. Even members of the bourgoisie acquired John of Wales' treatises (Suma de collations and Bre-viloqui) as a source of moral and political information. Finally, Francisco Eiximenis, the most important Catalonian political writer, made constant and ample use of the works of John of Wales, as attested to by his numerous and at times inacurate quotes, which can be clarified by referring to the Brevilo-quium and Communiloquium. In sumary, John of Wales' influence in medieval Catalonia was widespread and profound: it reached not only the higher political echelons of society, and the lower ranks of the middle class, but also the most remote places of the Valentian-Aragonese region of the Maestrazgo.