Youth crime in the United States remains near the lowest levels seen in the past three decades, yet public concern and media coverage of gang activity has skyrocketed since 2000. Fear has spread from neighborhoods with longstanding gang problems to communities with historically low levels of crime, and some policy makers have declared the arrival of a national gang “crisis.” Yet many questions remain unanswered. How can communities and policymakers differentiate between perceived threats and actual challenges presented by gangs? Which communities are most affected by gangs, and what is the nature of that impact? How much of the crime that plagues poor urban neighborhoods is attributable to gangs? And what approaches work to promote public safety?