Description:Students of Celtic literature are agreed that the 'Mabinogi' has been influenced in its form and content by Irish literature and tradition, but opinion differs considerably on the question of the extent of such influence. The present work devotes itself primarily to a study of the Irish affinities of the second Branch, 'Branwen', and proceeds to an analysis of the general structure of the tale.The author maintains that the borrowings in 'Branwen' from Irish literature are extensive; that the tale is later than the other three and is not rooted so firmly in Welsh mythology, folklore and tradition; and suggests that it was composed towards the end of the eleventh century by a literary artist steeped in Irish literature. This detailed examination, and especially the comparisons drawn between numerous elements in Branwen and themes in Irish literature, provides a significant contribution to the study of the 'Mabinogi'.