Changes in the family structure can be very disruptive to adolescents who live in those families. This article examines the impact of the number of family transitions on delinquent and drug-using behavior. Specifically, the effect of family transitions is hypothesized to be mediated by problems within the family, school, and peer settings. A sample of 646 boys (73%) and girls (27%) taken from a longitudinal panel study of high-risk adolescents are used to examine these hypotheses. For girls, little support is found for the direct or the indirect effect of family transitions on delinquent behavior or drug use. For boys, however, both forms of problem behavior are influenced by family transitions directly and indirectly through changes in, and problems with, peer associations. The findings suggest that during times of family turmoil, the friendship network of adolescent male children is also disrupted, leading to an increase in associations with delinquent others and, in turn, an increase in problematic behaviors.