Although social isolation has been posited as a critical structural mechanism linking neighborhood disadvantage to the reduced life chances of inner-city residents, there have been few empirical tests of this proposition. We examine the relative importance of neighborhood poverty and individual and family characteristics on social-network composition and community organizational participation of inner-city Chicago African American families. The results of the multilevel analysis indicate that, while most of the variation in isolation outcomes is due to individual-level respondent characteristics, social-network composition and some forms of organizational participation are affected by neighborhood poverty. Implications of the findings and directions for future research are discussed.