This chapter explores in detail Chaucer’s uses of the interjection allas in various prose and poetic texts. Chaucer’s many uses and contexts of allas suggest how the functions and significations of the Middle English interjection were not stable but rather shift according to who is speaking, where, to whom, in what narrative or textual situation. From the perspective of Bakhtin’s theory of dialogism, Chaucer’s poetic practice gives some concreteness to the grammarians’ theories of interjections, affect, and semantics in interpersonal and semiotic contexts.