This volume provides an overview of the economic literature on contract law. There follow 20 chapters, all written by experts in the fi eld. Each chapter off ers a thorough review of the literature, an extensive bibliography, and a personal refl ection on avenues of future research. Only seven of the 20 chapters are updated versions of chapters that appeared in the 2000 edition of the Encyclopedia of Law and Economics; the 13 other chapters are completely new. This is in line with the ambitious nature of the second edition of the Encyclopedia: to increase the coverage from fi ve to 12 volumes, and from 4,300 pages to nearly double that size. Contract law is one of the classic fi elds of law. It is also one of the fi rst studied by law and economics scholars. It started, in a sense, with Coase (1960), whose seminal article can be interpreted as a call to solve externality problems through contract law. In the late 1960s, Birmingham, Barton, and others started to analyze specifi c contract law doctrines (see, for example, Birmingham, 1969; Barton, 1972). The fi rst monographs on law and economics (Tullock, 1971; Posner, 1973) each devoted separate chapters to contract law. Since then, the literature has steadily grown. Remarkably, many of these contributions appeared in American law reviews – apparently more than for most other fi elds.