The article is devoted to a complex study of one of the most complex institutions of private International Law (PIL) - establishing the content of foreign legal norms. Normative basis of the study is the legislation of PIL of a number of foreign states, judicial practice of France, Great Britain, Sweden, USA and other countries. The research methodology is based on the application of methods of comparative analysis and comparative law. In its legal nature, the institution for establishing the content of foreign law is procedural and is implemented in the international civil process. As a rule, the proper establishment of content is not an easy task for a national law enforcement official. In addition, foreign law should be applied as it is interpreted and applied in its «native» court. This requirement causes the greatest difficulties in the process of its practical implementation. From the point of view of the involvement of the court in the process of establishing the content of foreign law and the relation to this right, three approaches can be distinguished: 1) active (legal); 2) intermediate (mixed); 3) passive (actual). The article concludes that the most correct and functional is the active (legal) approach.