Mild traumatic brain injury has been associated with higher prevalence of posttraumatic stress disorder (PTSD). The extent to which head injury or loss of consciousness predicts PTSD is unknown. To evaluate the contribution of head injury and loss of consciousness to the occurrence of PTSD, we made a longitudinal evaluation of 1,260 road accident survivors admitted to the emergency department with head injury (n = 287), head injury and loss of consciousness (n = 115), or neither (n = 858). A telephone-administered posttraumatic symptoms scale inferred PTSD and quantified PTSD symptoms at 10 days and 8 months after admission. The study groups had similar heart rate, blood pressure, and pain levels in the emergency department. Survivors with loss of consciousness and head injury had higher prevalence of PTSD and higher levels of PTSD symptoms, suggesting that patients with head injury and loss of consciousness reported in the emergency department are at higher risk for PTSD.