This book attempts to provide an analysis of a number of different constructions in Welsh within the Government and Binding theory of Chomsky (1981) and subsequent work. In recent years, the Celtic languages have provided a fruitful area of research in particular with regard to the typological adequacy of a number of fundamental proposals in GB theory. The specific focus of this book is the role of agreement phenomena and the specification of empty categories. For the most part, I have assumed 'standard' GB analyses, providing discussion and definitions where I have made alternative proposals. For this reason, the book contains no overview of the basic components of GB. In many cases, my analyses build on those proposed elswhere in the literature for the Celtic languages, and I discuss a number of these in some detail for completeness. The book is organised as follows. Chapter One lays the basis for subsequent investigation of a number of interrelated phenomena by providing a detailed discussion of the basic clause structure of Welsh. I argue that despite the surface VSO characteristics of Welsh, the structure of clauses involves a VP node at both D-and S-structure. Chapter One also proposes a rule of V-fronting to INFL, the application of which is conditioned by the feature specification of INFL. Later chapters investigate the properties of the associated V-trace with respect to government.