Despite abundant literature on transaction costs, there is little to noin-depth analysis regarding what the transaction is or how it works. Drawing on both Old and New Institutional Economics and on a variety of interdisciplinary sources, this monograph traces the history of the meaning of transaction in institutional economics, mappingits topicality and use over time. Thismanuscripttreats the idea of ‘transaction’ as a construct with legal, competitive and political dimensions, and connects different approaches within institutional economics. The book covers the contributions of key thinkers from different schools, including (in alphabetical order) Ronald H. Coase, John R. Commons, Robert Lee Hale, Oliver Hart, Mancur Olson, Thorstein Veblen and Olver E. Williamson. This book will be of interest to advanced students and researchers of institutional economics,law and economics, and economics, and the history of economic thought.