It examines their reasons for joining gangs; their codes of conduct; their loyalty to the gang; the role of their leaders; and their criminal activities, many of which are performed on behalf of adult criminal organizations. It also describes the efforts of law enforcement officials and community workers to redirect gang members' energies into more constructive channels. Sister Falaka Fatah's House of Umoja in Philadelphia is cited as an example of citizen initiative, which is this case has dramatically reduced gang violence in the city. The project now functions as a group home for delinquent teenagers as well as a community center where former gang members receive job training. The information presented draws heavily on interviews with gang members and their families, with plainclothes police officers who work in special gang units, and with community activists. Photographs, an index, and 44 references are given. (Author abstract modified)