The dissertation examines the interpretation of the concepts of likelihood of confusion and dilution in the area of trademark law. These concepts are of critical importance to trademark law; their interpretation is largely dependent upon several complex, oftentimes ambiguous legal principles. For a long time the general consensus was that the foundation of trademark protection was the prohibition of trademarks that ran the risk of giving rise to confusion regarding the commercial origin of the goods and services. During the 20th century, this basic principle regarding the objective of trademark protection was gradually refined; for example, the introduction of the concepts of dilution and association broadened the traditional emphasis on origin, which nonetheless remains at the core of trademark law. The principle of confusion of origin, which indirectly protects consumers from deceptive practices, has been consistently upheld by the Swedish Supreme Court. The Court has been more tentative, however, with regard to the relevance, in the determination of the scope of trademark protection, of factors such as association and dilution. The European protection of trademarks represents a more expansive view of the objectives of trademark law. Having once been the sole basis of trademark law, the principle of confusion of origin finds itself merely at the core of an entire body of protective rules, which, moreover, stress the importance of the trademark’s role in modern advertising—rules sprung from the principle of protection against detrimental use or unfair advantage. According to the principle of characterising force, which is upheld by the European Court of Justice, the scope of protection is related to the earlier trademark’s distinctiveness. This principle confers on the issue of likelihood of confusion the character of a question of law. The complex nature of the determination of the boundaries of trademark protection implies that the concepts on which these boundaries depend take on a precise juridical meaning that differ from the everyday sense of the words. Well-known trademarks enjoy protection against unfair advantage or detrimental use. The European Court of Justice has ruled that this extended protection does not presuppose likelihood of confusion. Thus, the protection of well-known trademarks exists in its own right; it is not merely dependent upon the principle of confusion of origin.