It is hypothesized that collective efficacy, defined as social cohesion among neighbors
combined with their willingness to intervene on behalf of the common good, is linked to
reduced violence. This hypothesis was tested on a 1995 survey of 8782 residents of 343
neighborhoods in Chicago, Illinois. Multilevel analyses showed that a measure of collective
efficacy yields a high between-neighborhood reliability and is negatively associated
with variations in violence, when individual-level characteristics, measurement
error, and prior violence are controlled. Associations of concentrated disadvantage and
residential instability with violence are largely mediated by collective efficacy.