The Adolescent Antisocial Behavioral Check List (AABCL) is a behavioral scale consisting of 350 items that sample the extent of antisocial behavior manifested by delinquents in an institutional setting. The sample consisted of 30 males and 25 females (38 of whom were white) referred primarily by the juvenile court to the Illinois State Psychiatric Institute. Three tests were conducted to determine the validity of the checklist. Detailed analysis, which used multiple correlation techniques and included adjustments for the effects of sex, age, and social class, showed a strong relationship between the Impulsivity Index (as measured by Rorschach and Wechsler IQ scores) and AABCL-measured violent behavior. The relationship between violent behavior and reactivity to color on the Rorschach was particularly strong. Impulsivity was not associated with nonviolent behavior as measured by the AABCL. Results also showed that more violent boys rate themselves as emotionally healthier and better adjusted than do less violent boys, while more violent girls rate themselves as less emotionally healthy and well adjusted than their counterparts. Finally, a double-blind study of the effect of dextroamphetamine sulphate on a hyperkinetic delinquent patient showed that the target patient exhibited significantly more antisocial behaviors during the placebo period than during either the baseline drug period or the 2-week postplacebo drug period, while differences between the active drug period and the prestudy period were not significant. Tabular data, the checklist, 2 notes, and 25 references are provided.