The social composition of the local areas was determined through seven sociodemographic indicators drawn from census materials and aggregated to the local community level: percentages of nonwhites; foreign-born whites; male labor force unemployed; professional, technical, and kindred workers; owner-occupied dwellings; households with more than one person per room; and the median education level. The dimensionality of the sociodemographic indicators was restricted to that produced by a principal, two-factor solution. The study also analyzed the delayed and immediate interactions of delinquency rates and sociodemographic variables. One finding with significance for theory development is that delinquency rates were not simply the outcome of ecological processes in large urban areas. Rather, at least in Chicago, they were important components of that process, greatly accelerating neighborhood transition. Increasing delinquency rates apparently precipitated the departure of higher income residents from involved neighborhoods, tending to leave a higher percentage of low-income nonwhites in those neighborhoods. The study also indicates the importance of grounding ecological theories of crime and delinquency more fully in broader studies of urban change. 4 tables and 7 footnotes.