This study echoes and extends understanding of behavior problem risk of drug problems. Consistent with prior studies, children with both aggression and inattention/hyperactivity were at markedly increased risk compared to children with inattention/hyperactivity alone. However, the methodology of this study clarified that in a sample at significantly increased risk of drug problems, increased childhood inattention/hyperactivity also predicted earlier adolescent onset of drug use, independent of aggression. Problem behaviors in childhood, such as aggression, inattention, and hyperactivity, have repeatedly been linked to subsequent adolescent substance use and abuse. However, much ambiguity remains regarding whether attention problems related to attention-deficit/hyperactivity disorder (ADHD) as well as aggression (related to conduct disorder) are independently related to the emergence of substance abuse. This study disaggregated these two domains developmentally and examined the relation between childhood behavior trajectories and adolescent substance use. A total of 335 children of alcoholic and nonalcoholic fathers were studied prospectively. It was hypothesized that early indicators of substance abuse, such as early onset of drunkenness and drinking problems, would be increased in the behavior problem classes compared to the healthy class and that both inattention/hyperactivity and aggression problems would be significant predictors. Figures, table, and references