My doctoral research concerns the use of song within narrative works in the Middle Ages. I have concentrated first on the substantial tradition in Old French of incorporating songs in this manner; and second, on the importance of this tradition to Chaucer, a poet who includes songs in nearly all his narrative poetry, and who was deeply familiar with many of the late thirteenth- and early fourteenth-century French works of this type. In order to demonstrate the connection between this very large range of French narratives and Chaucer, it has been necessary first to define the French tradition on its own terms, since even by French scholars it has rarely been treated collectively, and some of the works have barely been explored. This assessment of the French material has involved a fresh attempt to define the lyric interpolations themselves, when (as in the majority of thirteenth-century works) they take the form of brief snatches of song known as refrains. Since the nature of these refrains has been a source of controversy among French scholars, my study begins by analysing them both as texts and as melodies, in order to assess their status and function within the narratives. I then go on to discuss works ranging from Jean Renart's Guillaume de Dole to Adam de la Halle's Le Jeu de Robin et Marion, to the dits amoureux of Machaut and Froissart. The influence of this French tradition upon Chaucer is examined first of all in Chaucer's early poems, through his direct knowledge and assimilation of Machaut and Froissart and other contemporary French poets. It is then traced, more indirectly, through Chaucer's reading of Boccaccio and Boethius. I thus consider Chaucer's use of Boccaccio's Il Filostrato in the light of Boccaccio's own knowledge of this French tradition from his position in the Angevin court of Naples. In addition, by investigating French translations of Boethius's De Consolatione Philosophiae, I examine the structural importance of this work as a prosimetrum both upon French narratives containing songs, and upon Chaucer's Troilus and Criseyde. In this way I aim to show that the influences upon his practice of combining lyric and narrative are both multiple and multiply connected. The aim of this dissertation is therefore two-fold: first, to contribute to the understanding of a substantial but little-known area of French studies, and second, to renew the discussion of Chaucer's relation to French love poetry by seeing his work as a late medieval development in England of a distinctive, and distinctively French mode of composition. Throughout the course of my work, my wider interest is in the way in which the juxtaposition of the two categories of lyric and narrative shows us that our understanding of medieval genre is in need of refinement. In particular, by taking account of the presence of musical notation in the manuscripts of several of the French narratives, I hope to suggest that some of our assumptions about the 'literary' nature of medieval genres should be revised, especially as works of this type often seem composed precisely in order to create and exploit contrasts of genre of a musical, as well as a poetic kind.