Although the degree of international cooperation in response to transnational crime has increased significantly over the past 20 years, many gaps in cooperation still exist that can be exploited by criminals. The rationale for international cooperation to deal with transnational criminal organizations is powerful. These organizations are becoming stronger and more diverse and are more frequently engaging in systematic forms of cooperation to further their criminal activities, extend the reach of illicit markets, and infiltrate legitimate business. The challenge posed by transnational organized crime can only be met if law enforcement authorities display the same ingenuity and innovation, organizational flexibility, and cooperation that characterize criminal organizations. Law enforcement cooperation should attempt to identify and immobilize criminals, disrupt organized crime activities, deprive criminal organizations of assets obtained through illicit activities, and dismantle the organizations themselves. Factors that inhibit and enhance international cooperation are identified. Informal methods of cooperation are discussed, including personnel exchanges, information sharing, bilateral and multilateral task forces, and strengthening law enforcement capabilities. Formal methods of cooperation are also addressed, such as facilitating extradition and encouraging mutual assistance. 45 notes