The current program of research aims to apply principles of social identity and social categorization theories to the pernicious problem of street gang affiliation among urban youth in the United States and Central America. A series of studies testing factors that may inadvertently promote gang association as well as factors that may help discourage gang association are underway. A spin-off from this effort includes the development of an assessment designed to identify youth at risk for joining street gangs that can be used to target prevention services toward youth most in need. Parts of this research take place in the context of regional efforts to prevent or suppress gang membership, delinquency and criminal offending. Applied contexts included in this work vary from neighborhood gang injunction policies to local gang prevention and gang intervention programs.