The American Street Gang provides a detailed accounting, through statistics, interviews, and personal experience, of what street gangs are, how they have changed, their involvement in drug sales, and why we have not been able to stop them. Klein has been studying street gangs for more than thirty years, and he brings a sophisticated understanding of the problem to bear in this often surprising book.

In contrast to the image of rigid organization and military-style leadership we see in the press, he writes, street gangs are usually loose bodies of associates, with informal and multiple leadership. Street gangs, he makes clear, are quite distinct from drug gangs - though they may share individual members. In a drug-selling operation tight discipline is required - the members are more like employees - whereas street gangs are held together by affiliation and common rivalries, with far less discipline.

With statistics and revealing anecdotes, Klein offers a strong critique of the approach of many law enforcement agencies, which have demonized street gangs while ignoring the fact that they are the worst possible bodies for running disciplined criminal operations - let alone colonizing other cities. On the other hand, he shows that street gangs do spur criminal activity, and he demonstrates the shocking rise in gang homicides and the proliferation of gangs across America. Ironically, he writes, the liberal approach to gangs advocated by many (assigning a social worker to a gang, organizing non-violent gang activities) can actually increase group cohesion, which leads to still more criminal activity.

And programs to erode that cohesion, Klein tells us from personal experience, can work - but they require intensive, exhausting effort.