This book provides an introduction to Generalised Phrase Structure Grammar (GPSG) and Head-driven Phrase Structure Grammar (HPSG), theories which have formed one of the main currents in syntactic theory since 1980. GPSG enjoyed considerable influence in the mid 80s, and HPSG has had a growing impact in recent years. Both frameworks have been influential not only in theoretical linguistics but also in computational linguistics. They contain a rich body of ideas which deserve the attention of anybody interested in syntax. The book is aimed at advanced undergraduates and postgraduates and assumes no prior knowledge of GPSG. Each of the thirteen chapters includes notes and exercises.