'Th'ende is every tales strengthe . . .' as Pandarus tells Criseyde, and the Canterbury Tales as a whole and in many of its parts - as well as some of Chaucer's other works - suggest both the significance and also the challenge and strain that Chaucer found in inventing an appropriate close to the structures that he had created in his poems. This essay outlines Chaucer's characteristic uses of such literary structures, and the particular place of an ending as the 'strengthe' in the distinctive forms of artistic wholeness that Chaucer's poetic structures represent. It is not only in Chaucer's many poems that are not brought to a close - the House of Fame, the Anelida, the Legend of Good Women, the Cook's Tale, the Squire's Tale - but also in those works where Chaucer does provide a conclusion, such as the ending of the Troilus or the ending of the whole Canterbury Tales with the Parson's Tale, that the poet's sense of the ending as a difficult and special part of the 'strengthe' of a literary structure is felt.