This book explores the interface between syntax and the other components of the grammar, in particular phonology, morphology, and argument structure. The author proceeds through a consideration of case studies, such as clitics and complex predicates (auxiliary and modal verbs) in Romance, grounding theoretical analysis in constant exemplification. She shows that a careful analysis of their properties can lead to a better understanding of the interaction of the various components of the grammar. The syntactic properties of clitics are considered in relation to their phonological and morphological characteristic. The properties of auxiliary verbs are analysed from the perspective of the interface between argument structure and syntactic structure. Modal verbs are examined at the interface between syntax and phonology. The analyses of clitics and auxiliaries throw interesting new light on the link between Romanian and Balkan/Slavic. This is a valuable contribution to the study of grammatical interfaces and to Romance verbal typology and comparative linguistics.