Objective: To examine the prevalence of acute stress disorder (ASD) and posttraumatic stress disorder (PTSD) in injured children and to evaluate the utility of ASD as a predictor of PTSD. Method: Children hospitalized for injuries sustained in a traffic crash were enrolled in a prospective study. ASD was assessed in 243 children within 1 month after injury, and PTSD was assessed in 177 of these children 3 or more months after injury. The relationship between ASD and PTSD was examined via correlations between symptom severity scores and calculation of sensitivity, specificity, and positive and negative predictive values for categorical prediction of PTSD from ASD or subsets of ASD symptoms. Results: Eight percent of children met the symptom criteria for ASD and another 14% had subsyndromal ASD; 6% met the symptom criteria for PTSD and another 11% had subsyndromal PTSD. ASD and PTSD symptom severity were associated. Sensitivity was low for prediction of child PTSD from child ASD. Subsyndromal ASD was a more effective predictor of PTSD. Conclusions: A substantial minority of injured children are affected by traumatic stress disorders. ASD in children may not be an optimal categorical predictor of PTSD. With increasing attention to early posttrauma services for children, empirically valid assessment/triage models deserve further study.