Conceptual and measurement issues surrounding externalizing behavior problems and academic underachievement, the strength and specificity of the covariation between these domains, and the viability of explanatory models that link these areas are reviewed. In childhood, inattention and hyperactivity are stronger correlates of academic problems than is aggression; by adolescence, however, antisocial behavior and delinquency are clearly associated with underachievement. Whereas investigations with designs that allow accurate causal inference are scarce, unidirectional paths from 1 domain to the other have received little support. Indeed, the overlap of externalizing problems with cognitive and readiness deficits early in development suggests the influence of antecedent variables. Low socioeconomic status, family adversity, subaverage IQ, language deficits, and neurodevelopmental delay are explored as possible underlying factors.