Criminologists have often assumed that the development of gangs is most likely in unstable, institutionally weak lower-class neighborhoods. However, gang activity also has been noted in relatively stable lower-class areas that are fairly well organized. Three classes of theories have developed to account for these phenomena. A systemic approach grounded in the theory of social disorganization has been the traditional explanation for the existence of gangs in the unstable areas, while the presence of gangs in the second type of neighborhood has usually been explained either in terms of subcultures that support such behavior or, more recently, in terms of economic marginalization. However, a fully systemic model that considers the private, parochial, and public orders of control can account for the processes described by each set of theories in a logically consistent manner. Notes and 63 references