The construct validity of a retrospective self-report measure of early childhood aggression, the Early Experience Questionnaire (EEQ), was assessed in a sample of substance abusing volunteers for drug studies at a research center in Baltimore. In contrast to the diagnosis of Antisocial Personality Disorder (APD), EEQ scores were not only associated with adult aggression, criminality, and substance abuse, but were also highly correlated with a cluster of measures reflecting emotionally reactive impulsivity. Correlations of the EEQ with the Minnesota Multiphasic Personality Inventory confirmed earlier findings obtained on a sample of alcoholics. Over and above the predictive influence of APD, early childhood aggression had some predictive influence on the incidence and severity of substance abuse but a substantial influence on the prediction of criminality.