The first important federal American antitrust law, the Sherman Act, prohibits any trust, contract or conspiracy in restrain of domestic or foreign trade. The interpretation of this statue has been governed by the use of the 'rule of reason'. The rule divides violations into two categories: those that are illegal per se and those that are to be defined as illegal only if they are unreasonable. The second important antitrust law is Clayton Act, passed in 1914. It prohibits any forms of market discrimination which could be harmful to fair competition. Another important regulation is the Federal Trade Commission Act and some other acts that the authoress briefly described in the article. As far as European antitrust law is concerned, there are few basie European regulations, whereas some areas are also regulated by the law of each of the member countries, so that both parties cooperate in antitrust cases. The most important regulations in the European Law are article 81 et seq. of the European Community Treaty. Their goal is to provide a system ensuring that competition in the internal market is not distorted (Art. 3(g) of the EC Treaty). Article 81 sets a generał rule prohibiting any agreements that could affect trade between member states. Article 82 prohibits any abuse of dominant market positions within the common market. One of the most important executive laws is the Council Regulation nr 1/2003 which implementats the rules created in the above mentioned articles. Many exemptions from the generał rule prohibiting distortion of the fair competition are known in the European Law. Some of them are described in the article.