Research has demonstrated that even after controlling for individual level attributes, individuals who join gangs commit more crimes than do nongang members. Furthermore, the offending level of gang members is higher when they report being active members of the gang. Therefore, gang membership clearly facilitates offending above and beyond individual level characteristics. But what impact does the onset of gangs have on aggregate crime patterns? By exploring levels and patterns of crime in an "emergent gang city" (Pittsburgh, Pennsylvania), the authors test whether the individual level finding linking gang membership to increased offending equates to more crime at the aggregate, citywide level. They also explore the impact that gang formation has on local patterns of crime. Gangs tend to be territorial, but although many qualitative accounts describe the crime-gang relationship within the community, few empirical studies have explored how gangs shape the spatial distribution of crime in and around their territory. (Contains 2 tables, 3 figures, and 3 notes.)