Customary law has been the subject of intense debate and the issues arising from the intersection of customs and the law are far from settled. This research review brings together seminal work from scholars in law, economics and history. The first section analyses various perspectives on the history of customary law. Part two focuses on the commercial customary law and includes a number of case studies covering the role and limits of customary systems in a variety of commercial settings. The final section explores the role of custom in international law from a variety of legal and economic perspectives.