All these need to know the fundamental principles of contract law shared by the legal systems of the Member States and to have a concise, comprehensive and workable statement of them. The Principles of European Contract Law provides this.

The Principles have been drawn up by an independent body of experts from each Member State of the EU, under a project supported by the European Commission and many other organisations. The Principles are stated in the form of articles, with a detailed commentary explaining the purpose and operation of each article and its relation to the remainder. A particularly valuable feature is that each article also has extensive comparative notes surveying the national laws and other international provisions on the topic.

The Principles of European Contract Law Parts I & II covers the core rules of contract: formation, authority of agents, validity, interpretation, contents, performance, non-performance and remedies. The articles previously published in Part I (1995) are included in a revised and re-ordered form.