We found higher levels of positive soft neurological signs in PTSD participants than in participants who also experienced similar trauma but did not develop PTSD. This finding was replicated in two samples, that is, Vietnam combat veterans and adult female survivors of childhood sexual abuse, despite differences in gender, age, nature of trauma, and period of life when the trauma occurred. Past developmental history of participants and a substance abuse history of first-degree relatives also differentiated PTSD from non-PTSD groups in both combat and sexual abuse samples. Evidence for neurological impairment and compromised developmental history raises the possibility of pretrauma impairment as a risk factor for the development of PTSD.