BACKGROUND: There is still marked variability in the findings concerning psychiatric disorders associated with traumatic injury. The aim of this study was to determine the incidence of acute stress disorder (ASD) and posttraumatic stress disorder (PTSD) following accidental injuries, and to predict the PTSD symptom level at 6 months, taking into particular consideration the role of pre-existing psychiatric morbidity and insufficient command of the local language. METHOD: A total of 255 accident survivors who were hospitalized for at least 2 consecutive nights at a Swiss university hospital for treatment of recently acquired physical injuries were interviewed within 2 weeks of the trauma and 6 months after the accident. Patients who did not have a good command of German but were fluent in Italian, Spanish, Portuguese, Serbo-Croatian or Albanian were assessed using interpreters. The main outcome measure was the Clinician-Administered PTSD Scale. RESULTS: Ten patients (3.9%) were diagnosed as having ASD. At 6 months, 8 patients (3.1%) had PTSD. A regression model using 12 potential predictor variables explained 40% of the variance of PTSD symptoms; mild traumatic brain injury (p < 0.001), pain (p < 0.05), ASD symptom level (p < 0.001) and emotional coping (p = 0.001) predicted higher PTSD symptom levels, while high Sense of Coherence (p < 0.05) and perceived responsibility for the accident (p < 0.01) were associated with lower PTSD symptom levels at follow-up. CONCLUSIONS: ASD and PTSD seem to occur less frequently following accidental injuries than previously reported in the literature. Pre-existing psychiatric morbidity and lack of proficiency in the locally spoken language do not appear to play an important role in the development of PTSD.