The spatial distribution of crime in urban neighborhoods has long been a focus of criminological research. This body of research has consistently shown that where there are areas of high structural disadvantage (poverty, segregation, and residential instability), there are also high levels of crime. There is a growing consensus that the key mechanism linking structural disadvantage and crime is low levels of informal social control. Thus, it is crucial to examine why structural disadvantage gives rise to low levels of informal social control. The current study drew data from the 1995 Project on Human Development in Chicago Neighborhoods (PHDCN), to examine the contribution that social ties, legal cynicism, neighborhood attachment, and satisfaction with police make to neighborhood levels of informal social control and to discover the extent to which these variables mediate the relationship between structural disadvantage and informal social control. PHDCN participants were 8,782 Chicago residents who offered their assessments of the structural and cultural properties of their neighborhoods. Results of multivariate statistical analyses indicated that, after controlling for individual-level effects and ecological factors, neighborhood attachment and satisfaction with police were positively associated with neighborhood levels of informal social control. This reveals that when residents feel satisfied with their neighborhoods, they take more responsibility for maintaining order, and thus engage in informal social control. On the other hand, residents dissatisfied with their neighborhood are less likely to act in ways that promote informal social control processes. Results also indicated that a substantial proportion of the relationship between neighborhood structure and informal social control was mediated by satisfaction with police and neighborhood attachment. The findings suggest that strategies to increase informal social control in urban neighborhoods should focus on improving police-community relations. Tables, references