Teplin and colleagues¹made a methodologic advance by assembling a large sample of youth involved in the juvenile justice system to examine rates of psychiatric diagnosis. Unfortunately, their measurement overlooked posttraumatic stress disorder (PTSD), a condition that has been documented to occur at high rates among antisocial and incarcerated youth.^2-6 The absence of information on PTSD is striking given the authors' recognition that exposure to potential trauma (eg, maltreatment, neglect, and community violence) is an important risk factor for antisocial behavior and the development of psychiatric disorders.^7,8 Posttraumatic stress disorder also has clear relevance for their findings that show substantial depression, dysthymia, and substance abuse in the sample, as well as their recommendations regarding future research on patterns and sequences of comorbity. Epidemiologic evidence demonstrates that PTSD is accompanied by high rates of comorbid affective and substance use disorders, and suggests that exposure to traumatic stressors and development of PTSD often precedes the onset of these comorbid conditions and may be risk factors for them.^9-11 While the findings and recommendations by Teplin and colleagues stand on their own merits, they are limited to the extent that trauma and PTSD are major features of the lives of the young people they studied. We strongly encourage future researchers to include evaluation of exposure to trauma and PTSD so that a more comprehensive understanding of the mental health needs of criminally involved youth will emerge.