The sample of boys was representative of the California Youth Authority population. They received a standard psychiatric screen, a semistructured interview for PTSD, and a self-report questionnaire measuring personality traits and defenses. A nonclinical group matched for sex and age was used to compare psychometrics. It was determined subjects suffered from PTSD at higher rates than other adolescent community samples and at higher rates than those found in county probation camps. About 32 percent fulfilled the criteria for PTSD, and 20 percent fulfilled partial criteria. About half of the subjects described witnessing interpersonal violence as the traumatizing event. Psychometric results converged in the predicted way. Subjects with PTSD showed elevated distress, anxiety, and depression and lowered somatization, conversion, disassociation, and withdrawal. The authors conclude PTSD occurs at high rates in male juvenile delinquents and discuss implications of the findings for management and treatment. Personality characteristics that may put individuals at risk for the development of PTSD are identified. 38 references and 2 tables