This study, part of the long-range Project on Human Development in Chicago Neighborhoods, assesses the "broken windows" thesis and its implications for crime control policy and practice. The researchers propose that crime stems from the same sources as disorder—structural characteristics of certain neighborhoods, most notably concentrated poverty. "Collective efficacy," defined as cohesion among neighborhood residents combined with shared expectations for informal social control of public space, is proposed as a major social process inhibiting both crime and disorder in this NIJ Research in Brief (NCJ186049).