This study examined sibling relationships as a factor that determines the impact of parents' hostility on early adolescent internalized and externalized emotional distress. The interactional quality of the sibling relationship may mediate or moderate the relationship between parental hostility and adolescent distress by serving either as a 'buffer' for the adolescent when the relationship is warm and supportive or it may amplify the negative effect of hostile parenting if the sibling interactions also are conflictual and unsatisfying;The analyses were based on a sample of 221 sibling pairs from intact families participating in a larger study of families and economic hardship in a rural midwestern state. Each sibling pair includes a seventh grade child (mean age - 12.6 years) with an older sibling within 4 years of age. Both self-report data from the two siblings and observer-report data from videotaped family interaction tasks were used in the analyses. Latent variable structural equation modeling was used to estimate the hypothesized mediator and moderator family process models;Results indicated general support for the underlying hypothesis that the interactional quality of sibling relationships influenced the association between parental hostility and early adolescent distress. Specifically, hostility in the sibling relationships dyad mediated the impact of both mother's and father's hostility on adolescent externalized and internalized distress. The level of hostility between sibling did not appear to function as a moderator. Results concerning sibling warmth and support were mixed with no support for the mediation models and only modest evidence of a buffering effect if the older sibling demonstrated high levels of warmth and support. Parents hostility had a significant negative effect on warmth and support in the sibling relationship;Although results must be interpreted with caution due to their cross-sectional nature, the present findings are consistent with an accumulating body of evidence that siblings play important roles in children's lives. Behavior in the sibling relationship may contribute to the spread and containment of hostility within the family system and, in turn, help explain the consequences of those behaviors for adolescent adjustment.