Abstract
The paper deals with a traditional issue of private international law, in particular treatment of foreign law. Beside ascertaining the content of foreign law, it studies the treatment of foreign law in the light of the iura novit curia principle.
First, it compares the national approaches to these issues and analyses their relation to the differences between the judges' duties in civil law and common law countries. In the second part, it desribes the development of the unification efforts with respect to treatment of foreign law in relation to the concepts of civil procedure in various countries.