Trauma and posttraumatic stress symptoms increasingly are recognized as risk factors for involvement with the juvenile justice system, and detained youth evidence higher rates of trauma exposure and posttraumatic stress disorder (PTSD) compared to their nondetained peers. Using a sample of 83 detained boys aged 12 to 17, we tested the hypothesis that degree of PTSD symptomatology would be positively associated with arrest frequency and delinquency severity. Results indicated that 95% of participants had experienced trauma, and 20% met criteria for Full or Partial PTSD. As predicted, severity of PTSD symptoms was associated with degree of delinquency, and this effect remained present for the past year delinquency variables after controlling for the total number of traumas reported. (Contains 2 tables.)