Faster air service, more sophisticated telecommunications, electronic fund transfer, and political, economic, and social changes have made it easier for criminals to operate transnationally. Criminal law has remained almost wholly territorial, concerned only with acts or omissions that were committed in the territory of the forum state. Where formal cooperation in criminal cases is impossible, informal cooperation may arise. Such informal and unilateral actions are an unsatisfactory response to a growing problem. Unilateral action can create unnecessary tensions between nations. For the police to be able to work across borders, arrangements have to evolve on three different levels: the political level, the structural level, and the practical level. There are five trends in international cooperation currently taking place. The first is that international cooperation is strengthening with increasing rapidity. The second is the variation of intensity of international cooperation. Small groups of “fast track” countries are increasingly emerging. The third is that international cooperation is becoming formalized and “deeper,” with “soft” resolutions and recommendations being increasingly supplemented by treaties and joint decisions. The fourth trend is that international cooperation is developing from an ad hoc focus on individual offense categories or issues, to a more general international criminal policy. The fifth trend is that international cooperation is becoming increasingly politicized. Economic, social, and political factors have contributed to changes in the amount and structure of crime. These factors cannot be changed but their effects on crime and the control of crime can be influenced in order to lessen the amount and seriousness of crime. Many states are responding to their national crime problem by reviewing the effectiveness of their criminal policy and by setting up a variety of crime prevention councils and projects. International cooperation is broadening and strengthening to the extent that, in such areas as drug trafficking and organized crime, there is broad agreement on general goals. The different states will continue to have different views of the general role of criminal law in society. 37 footnotes