This article by Robert J. Sampson and W. Byron Groves tests the social-disorganization theory, which posits that low economic status, ethnic heterogeneity, residential mobility, and family disruption lead to community social disorganization, which in turn increases crime and delinquency rates. The study uses data from the British Crime Survey (BCS) to measure community-level structural factors and the mediating dimensions of social disorganization. The results support the theory, showing that between-community variations in social disorganization transmit much of the effect of community structural characteristics on rates of both criminal victimization and criminal offending. The study also examines the direct effects of community-level family disruption and urbanization on crime rates, finding that family disruption has a direct positive effect on the prevalence of street-corner teenage peer groups, while urbanization has a negative effect on local friendship networks. The findings highlight the importance of community social organization in mediating the effects of exogenous factors on crime rates.This article by Robert J. Sampson and W. Byron Groves tests the social-disorganization theory, which posits that low economic status, ethnic heterogeneity, residential mobility, and family disruption lead to community social disorganization, which in turn increases crime and delinquency rates. The study uses data from the British Crime Survey (BCS) to measure community-level structural factors and the mediating dimensions of social disorganization. The results support the theory, showing that between-community variations in social disorganization transmit much of the effect of community structural characteristics on rates of both criminal victimization and criminal offending. The study also examines the direct effects of community-level family disruption and urbanization on crime rates, finding that family disruption has a direct positive effect on the prevalence of street-corner teenage peer groups, while urbanization has a negative effect on local friendship networks. The findings highlight the importance of community social organization in mediating the effects of exogenous factors on crime rates.