This chapter discusses contract law. Ordinarily, market transactions do not involve infringements of deontological constraints. For this reason (and since they usually involve money or easily monetized goods), standard cost-benefit analysis is particularly apt for analyzing contract law. Nevertheless, it is argued that certain deontological constraints apply to contracting behavior and that combining deontological constraints with economic analysis of contract law, may be fruitful. The chapter briefly surveys the deontological constraints pertinent to contract law and critically examines the standard economic response to them. It then demonstrates how deontological constraints may be integrated with economic analysis of the contracting stage, focusing on the doctrines of mistake and misrepresentation. Last, it highlights the differences between economic and deontological analyses of contract performance and breach, and discusses the difficulties facing integration of deontological constraints with the economic analysis of contract remedies, given the current state of the pertinent theories.