This study was undertaken to examine the relative contribution of paternal history of substance abuse and difficult temperament in fathers and sons on a panel of individual, family, and interpersonal risk factors shown to be associated with deviant peer affiliations among boys. Deviant peer affiliations among boys have been associated with development of a conduct disorder and early age substance nse. In a sample of sons of substance abusing fathers (n = 56) and normal fathers (n = 94), a structural equation path analysis revealed that the conjoint influence of paternal history of substance abuse and difficult temperament in fathers and sons influenced family and interpersonal processes that, in turn, influenced the developmental trajectory of the child toward deviant peer affiliations. The full model (F = 74.49, p < .001, Stability Index = 0.70) explained 50% of the variance on sons' Peer Delinquency Scale scores. Implications for primary prevention are discussed.