Objective: This study evaluated the prevalence of posttraumatic stress disorder (PTSD) and the longitudinal course of early PTSD symptoms in survivors of terrorist attacks. It additionally assessed the effect of continuous terrorism on the course of early symptoms of PTSD. Method: Thirty-nine survivors of terrorist attacks and 354 survivors of motor vehicle accidents were evaluated upon admission to a general hospital emergency room and 1 week and 4 months later. Heart rate was measured upon admission to the emergency room. Peritraumatic dissociation was assessed at 1 week. PTSD symptoms, anxiety, and depression were measured at 1 week and 4 months. The Clinician-Administered PTSD Scale conferred a diagnosis of PTSD at 4 months. Additionally, the course of early PTSD symptoms during an era of frequent terrorist attacks (N=137) was compared with that seen during years of relative calm (N=256). Results: Survivors of terrorist attacks had higher rates of PTSD than motor vehicle accident survivors (37.8% versus 18.7%). The type of traumatic event, however, did not add to the prediction of PTSD from the emergency room heart rate, peritraumatic dissociation symptoms, and early PTSD symptoms. The longitudinal course of early PTSD symptoms was not affected by the greater frequency of terrorist attacks. Conclusions: Early symptoms are reliable risk indicators of PTSD across events and circumstances. Converging effects of terror-induced fear, adjustment, and resiliency might explain the lack of effect of intense terrorism on the course of PTSD symptoms.