Part I examines the definition of "crime" as the term is used in domestic law; such a definition supplies the criteria to be used in delineating the concept of international crime. Part II applies these criteria to produce a definition of "international crime." Part III completes the definition by discussing the various types of conduct that fall within the scope of the term "international crime." Part IV examines the extent to which criminal law in the United States currently provides for the prosecution of international crimes as thus defined. Part V concludes the article by considering various proposals for codifying the law on international crimes. The article concludes that the concept of crime can be projected into the international sphere only by analogy. Provisions of multilateral treaties requiring states to prosecute and punish particular forms of individual conduct do furnish a sufficiently close analogy to the prohibitions of domestic criminal law and, at least in a formal sense, can therefore be regarded as creating international crimes. 105 footnotes, appended provisions of United States law implementing international obligations to prosecute under multilateral conventions. 105 footnotes.