Crime is usually territorial. It is a matter of the law of the place where it occurs. Nevertheless, a surprising number of American criminal laws apply outside of the U.S. Application is generally a question of legislative intent, expressed or implied. In either case, it most often involves crimes committed aboard a ship or airplane, crimes condemned by international treaty, crimes committed against government employees or property, or crimes that have an impact in this country even if planned or committed in part elsewhere. Although the crimes over which the U.S. has extraterritorial jurisdiction may be many, so are the obstacles to their enforcement. Contents of this report: (1) Introduction; (2) Constitutional Considerations; (3) Conclusion; (5) Bibliography.