This article applies an individual-level routine activities perspective to explaining rates of delinquency. The theoretical analysis also links the opportunity processes of that perspective to key themes of social disorganization theory. Multilevel analyses of 4,358 eighth-grade students from thirty-six schools in ten cities support the central hypothesis: Time spent in unstructured socializing with peers has both individual and contextual effects that explain a large share of the variation in rates of delinquency across groups of adolescents who attend different schools. In addition, parental monitoring has a very strong contextual effect on unstructured socializing, which supports the proposed integration of routine activity and social disorganization perspectives.Although it is individual adolescents who engage in delinquent behavior, delinquency is not strictly an individual-level phenomenon. Rates of delinquency also vary across groups, such as networks of friends (Esbensen and Huizinga, 1993;Haynie, 2001), youth attending the same The authors are especially grateful to Finn Esbensen for access to these data and for his longstanding support for their work. Thanks also to Rich Felson, Phil Schwadel, Jennifer Schwartz, Brian Goesling and Eric Silver for helpful comments on earlier drafts.