The author initially reviews Shaw and McKay's ecological approach to social disorganization and delinquency which was developed under the assumption that Chicago was characterized by a stable set of ecological dynamics. Methods of measuring change in ecological models of crime and delinquency are described, as are the Chicago data used in this study -- male juvenile referral rates and measure of ecological change available from census materials. This analysis shows that Chicago's ecological structure has undergone significant changes since 1940. Areas characterized by the most rapid changes experienced dramatic increases in delinquency, which is consistent with the social disorganization perspective. Developments in some areas, however, differed substantially from the pattern predicted from the social disorganization model. This suggests that ecological theories should consider dynamics external to local communities, such as housing shortages and black migration, and must be careful in defining local communities. Tables and approximately 50 references. (Author abstract modified)