This study indexed the relationship between acute stress disorder (ASD) and subsequent posttraumatic stress disorder (PTSD) in injured children. Consecutive children between 7–13 years admitted to a hospital after traumatic injury (n = 76) were assessed for ASD. Children were followed up 6-months posttrauma (n = 62), and administered the PTSD Reaction Index. Acute stress disorder was diagnosed in 10% of patients, and 13% satisfied criteria for PTSD. At 6-months posttrauma, PTSD was diagnosed in 25% of patients who were diagnosed with ASD. Acute stress reactions that did not include dissociation provided better prediction of PTSD than full ASD criteria. These findings suggest that the current ASD diagnosis is not optimal in identifying younger children who are high risk for PTSD development.