This study is an application of Chomsky's minimalist program (1995) to the universally relevant phenomenon of auxiliarity, restricted here to verb auxiliarity. It provides detailed minimalist analyses of auxiliary verb constructions in two Romance languages (Italian and Sardinian). The theoretical framework is supplied by Generative Grammar, and in the course of the book a number of modifications to this framework are proposed. Approaches based on grammaticalization theory also play a role in the analysis and interpretation of auxiliary verbs.