The Franciscan Order was one of the most remarkable and influential forces in medieval and early modern Irish society. While the earlier and later phases of the movement have attracted the historian's notice, the remarkable second flowering, which occurred between 1400 and 1534, has not been explained until now. This study traces the reforming tendencies among the friars from the beginning of the fifteenth century to the eve of the Reformation. The most important group to emerge were the Observant friars, recognised as an independent body in 1460. The emergence of groups of lay people living according to the rule of the Franciscan Third Order is also fully explored as well as the developments among the Conventual (or unreformed) Friars. A major feature of this work is the emphasis placed on the lifestyle of the friars themselves. Particular attention is paid to their religious, liturgical and disciplinary practises, their educational and governmental structures and their impact as preachers and confessors as demonstrated by the material listed in the library catalogue of the Youghal Friary between 1490 and 1523. The first complete edition of this important and unique document is given as an appendix.