In this article, the important similarities and differences across criminal, deviant, and extremist groups are explored. Drawing from research on street gangs, this article explores issues such as levels of explanation, organizational structure, group process, and the increasingly important role of technology and the Internet in the context of radicalization. There are points of convergence across these groups, but it is important to understand the differences between these groups. This review finds little evidence to support the contention that American street gangs are becoming increasingly radicalized. This conclusion is based largely on organizational differences between gangs and terror groups.