“Principles of International Criminal Law” was first published four years ago and has been well received. It has since appeared not only in a second German edition, but also in Spanish, Italian and Chinese. Rapid developments in the field have now made a new English edition necessary. The worldwide interest in international criminal law is strong and ever growing. This is shown by, among other things, the proliferation of publications on the subject in recent years. While the ad hoc Tribunals for the former Yugoslavia and Rwanda will soon cease operations, the International Criminal Court is just getting in gear: The Court’s first decisions on important issues of procedural and substantive law are now available. Other forms of enforcing international criminal law, such as “hybrid” courts, have also assumed greater importance; at the same time, international criminal law has come increasingly to be implemented and enforced in domestic criminal law. Today, there are many indications that international criminal law will continue to develop rather than stagnate or even suffer reversals.