This book provides a general perspective on valency-changing mechanisms - passives, antipassives, causatives, applicatives - in the languages of the world. It contains a comprehensive typology of causatives by R. M. W. Dixon, and detailed descriptions of valency-changing mechanisms in ten individual languages by leading scholars, based on original fieldwork. The sample languages span five continents and every kind of structural profile. Each contributor draws out the theoretical status and implications of valency-changing derivations in their language of study, and the relevant parameters are drawn together, and typological possibilities delineated, in the editors' introduction. The volume will interest typologists, those working in the fields of morphosyntactic variation and lexical semantics, and exponents of formal theories engaging with the range of linguistic diversity found in natural language.