This study utilized psychophysiologic techniques to assess emotional arousal during imagery of psychologically traumatic experiences. All subjects were medication-free Vietnam combat veterans, classified on the basis of DSM-III-R criteria into groups with posttraumatic stress disorder (PTSD, n = 18) and no mental disorder (control, n = 15), which did not differ in extent of combat or in the judged severity of the traumatic experiences reported. "Scripts" describing each subject's combat experiences as well as other experiences were read to them in the laboratory, and they were instructed to imagine the events the scripts portrayed, while heart rate, skin conductance, and frontalis electromyogram were recorded. The PTSD subjects' physiologic responses to their combat scripts were markedly higher than the controls'. The combined physiologic variables identified PTSD subjects with a specificity of 100% and a sensitivity of 61%. The results demonstrate exaggerated physiologic arousal during recollection of traumatic experiences in PTSD.