Posttraumatic stress disorder or PTSDI is a psychiatric disorder of considerable prevalence and morbidity and can affect persons of any age and ethnic or socioeconomic background.2-10 It is, unfortunately, a far too common outcome of participation in war, affecting 15.2% of Vietnam theater veterans 20 years after the war." Its prevalence may be even higher in inner city communities exposed to compound community trauma. In one small northeastern city, it was found to affect 67% of adolescents frequenting a community medical clinic for routine preventive health care.lz Reducing exposure to trauma would obviously be the most effective and immediate means of controlling the induction of PTSD and should be given the highest social priority. Beyond such efforts, understanding the means by which the extreme stress of trauma is neurobiologically transduced to produce PTSD may help in its prevention and treatment. Clinical studies have yielded, thus far, important empiric findings on ways in which the neurobiology of persons with PTSD differs from that of normal controls and from that of individuals with other psychiatric disorders. The most robust findings include apparent increased baseline activation of the noradrenergic system13 and exaggerated noradrenergic responses to pharmacologic perturbation of that system,I4 decreased 24-hour urine cortisol l e v e l~, l~'~ opiate antagonist-sensitive increases in stress-induced analgesia?' apparent enhanced negative feedback in the hypothalamic-pituitary-adrenal axis increased circulating thyroid hormone levels,22 increased cerebrospinal fluid corticotropin-releasing factor:3 and diminished hippocampal volume as measured by magnetic resonance imaging.w26These findings are invaluable in guiding further scientific studies. For example, it would be useful to know if these neurobiologic characteristics are sequelae of threshold trauma in all individuals or only in those individuals predisposed in some way to the development of PTSD. It would also be useful to know if any of these characteristics could be premorbid and thereby predispose to PTSD symptom formation on exposure to trauma. It is also not clear whether or how these findings relate to specific symptoms of PTSD. Also, are they early manifestations of PTSD or do they develop over time? Indeed, if these neurobiological stigmata of PTSD can be 'Address for correspondence: Ann M. Rasmusson, M.D., Psychiatry Service/l16A, Connecticut VA Healthcare System, West Haven Campus,