A physiological hyperarousal state, which can be reactivated by traumatic stimuli, occurs frequently in patients with posttraumatic stress disorder (PTSD). The goals of this study were to determine whether physiological hyperarousal measured by increased heart rate is a specific response to reminders of a patient's own traumatic events or a more generalized hyperarousal state. Five brief videotape scenes of traumatic events (hurricane, auto accident, Cambodian refugee camp, domestic violence, and Vietnam War) were shown to two patient groups with PTSD (Vietnam veterans and Cambodian refugees) and three control groups (Vietnam veterans, Cambodian refugees, and non-patient Americans). Observations of subjects' behavior, subjective ratings of distress, and heart rate change were recorded and evaluated. The results indicated that Cambodians with PTSD had the most reactions as measured by behavior and heart rate changes. These tended to occur during all scenes, not just the specific Cambodian scene, indicating a general nonspecific arousal. The Vietnam veterans had the fewest changes implying an inhibition of response. The control groups were intermediate in physiological response. The response in PTSD patients to reactivation scenes is complex and probably relates to type and degree of trauma, as well as to culture.