International criminal law has during the last two decades developed into an established branch of public international law. The aim of the thesis is to elaborate on the special nature of international crimes (that is, war crimes, crimes against humanity and genocide) and to illuminate how the typical characteristics of international crimes have affected the content and functioning of international criminal law. The study starts from the assumption that the law is not merely reflecting what is regarded as central in international criminality, but also affects sentiments about relevance. An interdisciplinary approach is followed in the study, that is, even though the study is a legal study, special attention is given to historical and criminological viewpoints, and to more philosophical thinking about criminal law.