The analysis found that the presence of a head injury was not related to whether or not the juvenile detainee had ever been involved in moderate/severe violent offenses compared to only nonviolent or mildly violent offenses; however, when involvement in a severe violent offense was compared with involvement in less violent offenses (none, mild, or moderate), the presence of head injury was found to have a significant impact. Twenty percent of juvenile detainees with a head injury had committed a severe violent offense compared to 10 percent of juvenile detainees without a head injury. The severity of the head injury (measured by the period of time unconscious) was also found to be significantly related to involvement in serious violent offenses. The finding of a significant association between self-reported head injury and severe violent offending among juvenile detainees is consistent with findings for adult violent offenders. Head injuries increase the risk for violent behavior by impairing cortical control and lowering the threshold for violence or by adding to the burden of multiple stressors, thus weakening restraints that prevent violence. The psychological and educational assessment protocol was administered in each of New South Wales' nine juvenile justice detention centers. The measurement of head injuries relied on detailed retrospective self-reports of head injuries. Data were also obtained on substance use, criminal history, cultural background, and offense classification. 6 tables, 4 figures, and 37 references