This study examined the construct validity of the Dutch version of Buss and Perry’s Aggression Questionnaire (AQ) in 73 adolescent male offenders aged 12 to 18 years who were participating in a residential rehabilitation program. There was a strong positive association between the Hostility subscale of the AQ and psychological and physical symptoms. The nature of this connection was discussed. It was argued that the Hostility subscale measures some unique aspect of aggression that is not incorporated by the Physical Aggression, Verbal Aggression, or Anger subscales of the AQ. As expected, the AQ scales correlated significantly with trait anger, social desirability, and age. Furthermore, staff ratings of physical violence, verbal aggression, anger, and negative attitude were obtained for each subject. Correlations between the AQ scales and these ratings were low. Possible explanations for this unexpected finding are discussed. Finally, normative and internal structure data are presented. Aggr. Behav. 28:87–96, 2002. © 2002 Wiley-Liss, Inc.