The suicide rate among American adolescents between the ages of 14-25 has dramatically increased during the last 50 years, and this fact has been the focus of extensive social-scientific investigation. To date, however, research focusing on the joint effects of mental health, family, and contextual-level predictors on adolescents' suicidal behaviors is scarce. Drawing on Durkheim's classic macro-level approach to suicide and collective efficacy theory, we use data from the Project on Human Development in Chicago Neighborhoods (PHDCN) to examine the effect of informal social controls on adolescents' suicide attempts. Analyzing reports from 990 youth, we examine the hypothesis that neighborhood-level collective efficacy and family-level integration and social control independently affect suicide attempts. We also examine the extent to which they interact in their effects on suicidal behavior. Overall, results from multilevel logit models support the Durkheimian expectation that family attachment reduces the probability that adolescents will attempt suicide. The effect of collective efficacy is interactive in nature. Specifically, we find that collective efficacy significantly enhances the protective effect of family attachment and support on adolescent suicidal behaviors. We discuss findings within the context of social control theory. (Contains 3 tables, 1 figure, and 8 notes.)