An association between childhood aggression and risk for subsequent development of a substance abuse disorder is now well-accepted. In order to better understand the relationship between the presence of paternal substance abuse and aggression among their offspring, 10-12 year old sons of fathers with (n = 34) and without (n = 39) a history of a substance abuse disorder were contrasted on demographics, aggressivity, biological indices of reproductive maturation, and the presence of psychiatric diagnoses. In addition, personality factors, the potential for physical abuse, and psychiatric diagnoses were also ascertained among their fathers. Sons of substance-abusing fathers were found to be significantly more aggressive than sons of nonsubstance abusers. However, they also differed from comparison boys on the basis of SES and school grade attained, as well as the proportion with specific psychiatric disorders. Substance-abusing fathers differed from nonsubstance-abusing men in terms of personality factors and the presence of specific psychiatric disorders, including antisocial personality. They also showed significantly higher child abuse potential scores. A multiple regression analysis of factors contributing to aggression in the boys revealed that a paternal personality factor characterized by stress reactivity, alienation, and aggression was the most robust contributor to aggression among the boys. The boys' diagnoses of attention deficit disorder, oppositional defiant disorder, and lower household socioeconomic status were also significant predictors of aggressivity. Contrary to expectations, paternal, psychiatric diagnoses, substance abuse status, and potential for physical abuse were noncontributory. The results suggest potential mechanisms by which both aggression and risk for substance abuse may be transmitted from father to son.