BACKGROUND: Long-term data on post-traumatic stress disorder (PTSD) following accidents are scarce. AIMS: To assess and predict PTSD in people 3 years after severe accidental injury. METHOD: Severely injured patients were recruited consecutively from the intensive care unit (n=121) and assessed within 1 month of the trauma. Follow-up interviews were conducted 6 months, 12 months and 36 months later; 90 patients participated in all four interviews. Symptoms were assessed using the Clinician-Administered PTSD Scale. RESULTS: Post-traumatic stress disorder was diagnosed in 6% of patients 2 weeks after the accident, in 2% after 1 year and in 4% after 3 years. Robust predictors of later PTSD symptom level were intrusive symptoms shortly after the accident and biographical risk factors. There were individual changes over time between the categories PTSD, sub-threshold PTSD and no PTSD. Whereas PTSD symptom severity was low or decreased for most of the patients, some of them showed an increase or a delayed onset. Patients with persisting PTSD symptoms at 6 months and patients with delayed onset of symptoms are at risk of long-term PTSD. CONCLUSIONS: The prevalence of PTSD was low over the whole period of 3 years.