This chapter deals with the formal aspects of Chaucer’s verse craft. It discusses Chaucer’s mastery of rhyme and rhythm, and illustrates some of the stanza forms (rhyme royal, ballade, rondeau) that Chaucer deployed. It describes the metrical system behind both his octosyllabic lines and his pentameter lines, including the treatment of final e. Deviations from metrical norms, such as headless lines and enjambment, are discussed, but I argue that even perfectly regular iambic tetrameter and pentameter lines show variation, based on the degree to which linguistic stress approximates or modulates away from the metrical template. Particular attention is paid to Chaucer’s own comments about rhyme and the syllable count.