abstract:The most significant contribution of pope Gregory the Great (†604) to the doctrine of purgatory occurs in the Dialogues, a work of contested authenticity. The doubts raised in the 1980s over its genuineness have still not been dispelled and the thesis that it is a hybrid and inauthentic work is confirmed by a study of its teaching on post-mortem purgation. This appears to have to have been influenced by the extension of the system of tarriffed penance into the afterlife, a development first shown in the narrative of the vision of the Irish monk, Fursey, composed on the Continent in the 650s. The Dialogues as they have come down to us may be a work composed in England in the 670s, while its sections on purgatory form part of an ongoing debate about the nature of penance, intercession, and the afterlife.