In this talk I will explore some areas of overlap between morphological and prosodic typology. In particular, I will look at the interaction between polysynthesis and stress, both of which have the word as their fundamental domain of instantiation. The basic question I ask is this: what happens with lexical prominence when words become longer, more morphologically complex and, ultimately, more sentence-like? To address the issue, I will provide data on the stress system of Mapudungun (ARN, isolate), a canonical polysynthetic language, native to South America. I will argue that this language – as well as others on the polysynthetic spectrum – shows important sensitivity to morphological structure in its stress-assignment system. I will go on explore the implications of this, both from a diachronic and a typological perspective.