New York University law professor Chevigny looks for instructive patterns in the behavior of police forces in New York City, Los Angeles, So Paulo, Buenos Aires, Kingston, Jamaica, and Mexico City. The question that interests Chevigny (Police Power, 1969; Cops and Rebels, 1972), who has written extensively about police abuse for human rights organizations, is why some police forces are more prone to violence than others. He believes such an understanding is key to police reform. His conclusion in this thoroughly researched study is that ``police work reproduces and represents the larger social order, and . . . tolerance of violence reflects the relation between the government and its citizens.'' Thus, Los Angeles has a worse record than New York in part ``because a strong streak of western vigilantism . . . was absorbed into police conduct.'' One reason more than a thousand people are killed by the police in So Paulo each year is that Brazilian society divides the citizenry into ``the wild'' and ``the cultivated.'' Its police force, organized along paramilitary lines, is ``prone to use violence against a well-defined enemy,'' which in this case becomes the lower classes. Reform is coming slowly to cities like So Paulo as authorities realize that, as a form of lawlessness itself, such violence fails to give ballast to the state's authority. Further, people are learning that there is no correlation between police violence and a reduction in crime. On the other hand, there is a threat of increased police violence in America as ``rising economic pressures and the fear of crime . . . create a constant temptation to arbitrary violence as a supposed shortcut to order.'' Chevigny's book is dull going for the average reader but should be of intense interest to students of police power and practitioners of reform.