Fair trading, that is to say the idea of a fair market-behavioural standard in the pre-contractual relationship between business and consumers, has played a fundamental role in EC law since the very beginning of the Community. After early attempts at horizontal harmonisation failed, a piecemeal legislative approach was adopted, and has resulted in an inharmonious coexistence of numerous sectoral Community measures concerning fair trading. At the same time, the European Court of Justice has developed in its case law a general concept of fair trading on the basis of the EC Treaty provisions on free movement.The author provides a systematic and comprehensive analysis of primary law as interpreted by the European Court of Justice in its relevant case law and of Community legislation pertaining to fair trading. He demonstrates that the countless specific fair trading rules are based on a common general concept of fair trading. The author thus unveils a principle of fair trading in the acquis communautaire, which he defines not only in content but also in scope, proving it to be a general principle of Internal Market law. The interrelationship between fair trading and the functioning of the Internal Market is one of the central themes of the book, which, unlike other fair trading related analyses, attaches particular weight to the role of primary law.Finally, in the light of the previous findings a stand is taken on the current initiative to adopt a directive on unfair commercial practices, which is the latest manifestation of the recurring idea of horizontal harmonisation in this field.