Two issues little discussed in the generative literature are the internal structure of pronouns and what it is in Syntax that triggers pronominal reference. This monograph treats these two topics in detail and investigates whether pronominal (strong, weak and clitic pronouns) and related elliptical expressions can be given a unified syntactic representation. The answer, derived from a wealth of cross-linguistic evidence, is largely affirmative: pronominals include a semantically empty noun as part of their internal structure. The case of null subjects in 'pro-drop' languages is also examined and it is argued that they are not empty pronominal categories but, rather, the reflex of a 'verbal determiner'. Finally, using the internal structure of pronouns as a sort of 'litmus paper', the book explores the relationship between functional and lexical heads as well as the notions of selection and licensing in syntax, and offers new insights into the categorial status of functional categories.