States are increasingly accepting the idea of compulsory jurisdiction for the International Court of Justice and the Court has more cases on its docket than ever before. This monograph deals with the topic in a concise and accurate manner. Chapter I deals with basic general problems, such as the notion and bases of and the deci-sions on the ICJ jurisdiction. Chapter II presents the question of ICJ compulsory jurisdiction based on treaty provisions. The central issue, ie the ICJ compulsory jurisdiction based on the optional clause, is dealt with in Chapter III. After presenting specific questions, such as the essence of the declarations accepting the optional clause, the principle of reciprocity, reservations, and formal conditions, the author concentrates in this chapter on the characteristics of the legal system created on the basis of the optional clause.