THROUGHOUT HISTORY MOST gang members have been young males from poor families. Most have grown up in urban areas, and many are part of a racial or ethnic minority group that is not fully integrated in American society. Recent immigrants are popular targets for gangs that are recruiting new members.

However, not all gang members are poor, urban, or members of minority groups. Some are white suburban youths from middle-class families. A rise in racist "skinhead" gangs is a signal that the problems leading to gang membership are widespread in the United States. There has also been a rise in female gangs, though one study estimates that 90 percent of gang members are male.

On the surface, gangs provide young people with a sense of purpose. They promise a support system to kids with absentee parents, jobs to the poorly educated...