I thank the speakers of Yurakaré who have taught me their language for sharing their knowledge with me. I would furthermore like to thank Grev Corbett, Michael Cysouw, and an anonymous reviewer for commenting on earlier drafts of this paper. All remaining errors are mine. The research reported in this paper was made possible by grants from Prof. Pieter Muysken’s Spinoza project Lexicon & Syntax, the University of Surrey, the DoBeS foundation, and the Netherlands Organization for Scientific Research, for which I am grateful. Pronominal affixes in polysynthetic languages have an ambiguous status in the sense that they have characteristics normally associated with free pronouns as well as characteristics associated with agreement markers. This situation arises because pronominal affixes represent intermediate stages in a diachronic development from independent pronouns to agreement markers. Because this diachronic change is not abrupt, pronominal affixes can show different characteristics from language to language. By presenting an in-depth discussion of the pronominal affixes of Yurakaré, an unclassified language from Bolivia, I argue that these so-called intermediate stages as typically attested in polysynthetic languages actually represent economical systems that combine advantages of agreement markers and of free pronouns. In terms of diachronic development, such ‘intermediate’ systems, being functionally well-adapted, appear to be rather stable, and it can even be reinforced by subsequent diachronic developments.