In the modular linguistic theory assumed by many generative linguists, phonology and syntax are interconnected but fundamentally independent components of grammar. The effects of syntax on phonology are mediated by prosodic structure, a representation of prosodic constituents calculated from syntactic structure but not isomorphic to it. Within this overall architecture, I investigate the placement of weak pronouns in the Austronesian language Chamorro. Certain Chamorro pronominals can be realized as prosodically deficient weak pronouns that typically occur right after the predicate. I showthat these pronouns are second-position clitics whose placement is determined not syntactically, but prosodically: they occur after the leftmost phonological phrase of their intonational phrase. My analysis of these clitics assumes that lexical insertion is late and can affect and be affected by prosodic phrase formation-assumptions consistent with the view that the mutual interaction of phonology and syntax is confined to the postsyntactic operations that translate syntactic structure into prosodic structure.