Terrorist groups—both inside and outside the al Qaeda network—sometimes form mutually beneficial partnerships to exchange "best practices." These exchanges provide terrorist groups with the opportunity to innovate (i.e., increase their skills and expand their reach). Understanding how terrorist groups exchange technology and knowledge, therefore, is essential to ongoing and future counterterrorism strategies. This study examines how 11 terrorist groups in three areas (Mindanao, the West Bank and Gaza Strip, and southwest Colombia) have attempted to exchange technologies and knowledge in an effort to reveal some of their vulnerabilities. The analysis provides the Department of Homeland Security and other national security policymakers with insight into the innovation process and suggests ways that government policies can create barriers to terrorists' adoption of new technologies.