Ноте and foreign antimonopoly legisfation having been analyzed and different opinions formed in jurisprudence having been studied, an attempt to formulate the notions of «agreement», «coordinated activity» and «collective dominant position» is undertaken in the article. These notions being widely used in the antimonopoly legislation to qualify the joint anticompetitive practice of the economic enterprises, the authorp roves the necessity of adding them to the Act of the Republic of Belarus «About counteraction to the monopolistic activity and development of competition».