The relationship between the Hospital of St John and the kings of Aragon during the last two centuries of the Middle Ages has been the subject of in-depth analysis by Anthony Luttrell and María Bonet. 1 However, no such detailed studies have been carried out for the rest of the Spanish monarchies, and in the case of Navarre, only a single study has appeared, on the fourteenth century. 2 In this paper I shall attempt to broaden our knowledge of how relations between the Hospitallers and the Spanish kings evolved in the later Middle Ages by an examination of the ties between the Hospitallers and the kings of Navarre in the founeenth and fifteenth centuries based on documents from the archives of the Hospitaller priory preserved in the Archivo Histórico Nacional. 3