Before-and-after victimization surveys were conducted in experimental and control areas. This quasi-experimental design made it possible to control for many threats to valid inference. It also permitted the investigation of displacement and diffusion of benefits from experimental to adjacent areas. In Dudley, improved street lighting was followed by significant decreases in the prevalence and incidence of crime in the experimental area compared with the control area. In Stoke, four measures of crime were derived from the before-and-after surveys: the prevalence and incidence of victimization, the prevalence of known victims, and the prevalence of witnesses of crime. Taking the results from all four measures, there was a marked and significant decrease in crime in the experimental area, a somewhat lesser decrease in crime in the adjacent area, and no decrease or a slight increase in crime in the control area. The crime decreases in the experimental area were often significantly greater than in the control area, but rarely significantly different from the decreases in the adjacent area. In both Dudley and Stoke, the benefits of improved street lighting, in terms of decreased crime, greatly exceeded its costs. The tangible savings from crimes prevented more than paid off the full capital costs within one year. 6 tables and 26 notes