In the legal systems of the United Kingdom, passing off provides a common law cause of action against the imitation and appropriation of a business's reputation by a third party. As an integral part of British unfair competition law it enjoys continued high practical relevance, notwithstanding the progressive harmonization of industrial property law. Under this aspect, it is the focus of the publication to demonstrate the influence of the ongoing European integration on the development of passing off. The decisive factors here include the need for legal protection from unfair practices in the common market and the aditional protection granted by trade mark law and the law on comparative advertising against taking unfair advantage of the repute of a mark. Furthermore, the practical relevance of passing off in obtaining a Community Trade Mark is taken into account as well.