In this thesis concerning the protection of well-known trade marks against confusion in the European Community Trade Mark (CTM) and Japanese trademark systems, the author critically considers the difficulties in comprehensively defining ‘well-known trade mark’ in the relevant international trade mark instruments. After critical analysis of various definitions of both ‘trade mark’ and ‘well-known trade mark’, she undertakes a comparison of the definitions of the parallel concepts of ‘trade mark of repute’ and ‘syuchi-syohyo’, and also undertakes an assessment as to the extent to which these trade marks are protected against confusion and kondo in the CTM and Japanese systems, respectively. It is concluded that the protection of well- known trade marks against confusion in the CTM and Japan cannot be said to be completely clear, and the author identifies some areas for legal reform