Objective: We prospectively examined the relation between various peritraumatic responses (that is, fear, helplessness, horror, amnesia, and fright) and the development of posttraumatic stress disorder (PTSD) 2 months after a trauma. Method: Participants included 123 motor vehicle accident (MVA) victims consecutively hospitalized in a traumatology department for over 72 hours during a 16-month period. Between day 2 and day 5 of their hospitalization, a psychiatrist assessed the patients' peritraumatic responses and acute stress disorder (ASD). Two months after the accident, an experienced psychiatrist contacted the patients by telephone, and the PTSD symptoms and the diagnosis were assessed with a modified version of the Clinician-Administered PTSD Scale (CAPS). Results: Of the participants, 48 reported an immediate fright reaction when faced with the prospect of their own death. Participants who reported a fright experience had a 17 times greater risk of subsequently meeting the diagnostic criteria for PTSD (odds ratio 16.75). A fright reaction predicted PTSD development with a specificity of 0.93 and a sensitivity of 0.60. Conclusion: The immediate reactions described in criterion A2 of the DSM-IV (that is, fear, helplessness, and horror) did not seem to be equally relevant. An initial feeling of fright seems to be an essential qualitative factor in the clinical description of psychological trauma.