Researchers have identified "collective efficacy" as a variable linked to the quality of life in a neighborhood. Collective efficacy is "the cohesion among residents combined with shared expectations for the social control of public space." This variable is a reliable predictor of a neighborhood's level of crime and disorder. This article portrays neighborhoods as developing groups characterized by the following stages: "dependence," in which the group depends on a leader for direction; "conflict," during which group members disagree among themselves and with the leader about goals and tactics; and "interdependence," a stage in which the group has resolved its conflicts and members are working together toward common goals. The authors explain how these stages of group development apply to neighborhoods. They then discuss how the characteristics of neighborhoods are linked to their crime levels. "Strong" neighborhoods have residents that interact interdependently on issues of community disorder; "vulnerable" neighborhoods have low rates of crime and disorder, but also feature minimal levels of neighborhood development and interaction; "anomic" neighborhoods have a high rate of crime and a low level of neighborhood development, depending on police to deal with community safety problems; and "responsive" neighborhoods, which have high levels of crime and disorder, but residents work cooperatively with police to resolve problems. This article explains how "situational policing" tailors the style of community policing to these various types of neighborhoods in order to promote collective efficacy. 9 notes