Earlier empirical studies on valency have looked at the phenomenon either in individual languages or a small range of languages, or have concerned themselves with only small subparts of valency (e.g. transitivity, ditransitive constructions), leaving a lacuna that the present volume aims to fill by considering a wide range of valency phenomena across 30 languages from different parts of the world. The individual-language studies, each written by a specialist or group of specialists on that language and covering both valency patterns and valency alternations, are based on a questionnaire (reproduced in the volume) and an on-line freely accessible database, thus guaranteeing comparability of cross-linguistic results. In addition, introductory chapters provide the background to the project and discuss its main characteristics and selected results, while a series of featured articles by leading scholars who helped shape the field provide an outside perspective on the volume’s approach. The volume is essential reading for anyone interested in valency and argument structure, irrespective of theoretical persuasion, and will serve as a model for future descriptive studies of valency in individual languages.