The research involved collecting the same data in different social contexts where gang members might be expected to operate: adult and juvenile correctional facilities; and community programs, such as alternative high schools, gang prevention programs, and private day jail programs. Data were collected in California, Illinois, Iowa, Michigan, and Ohio. Analysis showed that gangs seemed to function like a union guild for the underground economy. Members paid dues, attended meetings, had rules to live by, maintained treasuries, provided small welfare support payments to members in jail, and retained private attorneys. Gangs operated a wide variety of cash businesses and had several legal and illegal income sources. Gangs differed with regard to organizational sophistication, but higher-level gangs which were more organizationally sophisticated appeared to have a number of formal economic functions and capabilities as well. Most gangs were of the most sophisticated type and had formal rules. Gang members included both youth and adults, but top gang leaders were primarily adults with a long tenure in the gang. The underground economy of gangs involved such illegal items as semiautomatic pistols, ammunition cartridges, shotguns, revolvers, cocaine, and marijuana. Characteristics of gang members are analyzed in detail, as well as gang alliance systems and identities. Appendixes contain the survey instrument, a list of gang names in the study sample, internal records of a major Chicago gang, and advice to teenagers about gangs. References, endnotes, and tables