Although studies indicate that the vast majority of delinquency is committed in groups, evidence of reported membership in gangs is difficult to establish. Studies also indicate that gangs are primarily an inner-city slum phenomenon. One variant, however, is the transitional slum characterized by high residential mobility. The second variant is the stable slum in which population shifts are minimal. It has also been found that ganging has always been a predominantly male activity, with male gang members outnumbering female members about 10 to 1. It is suggested that major causes of gang delinquency are: (1) status frustration, (2) differential opportunity, (3) lower class culture, and (4) group process. Further studies treating gang delinquency as a variable rather than a phenotype are recommended. Six notes and 79 references are listed.