This collection of recent work in Head-Driven Phrase Structure Grammar focuses on interfaces between different grammatical components. The constraint-based formalism of HPSG and its specification of well-formed signs means that all grammatical information is encoded in a single feature structure. This provides the means for constructing elegant accounts of interactions between linguistic information at different levels, whether prosodic, morphological, syntactic, semantic or pragmatic. The fifteen papers in this volume explore interface phenomena in one way or another within HPSG with respect to a range of constructions and languages and between various grammatical components. The following topics are addressed: the relationship between constituent structure and prosodic phrasing both in English and in Japanese, the prosodic effects of pragmatically conditioned noun incorporation in Danish, auxiliary contraction in English, pronominal affixation in European Portuguese, the morpho-syntax of relative clauses in Lai, syntactic and semantic aspects of Korean relative clause formation, the analysis of illocutionary force in HPSG, the semantics and pragmatics of tense, the role of argument structure at the syntax-semantics interface with respect to German word-order, Dutch R-pronouns and Spanish psychological predicates, long-distance case assignment and negation in Welsh.