 The proposed study has three distinct but related research objectives. The first research goal is to measure psychophysiological correlates of treatment gains associated with Prolonged Exposure PE therapy for PTSD in veterans of Operations Enduring Freedom and Iraqi Freedom OEFOIF. Specifically, heart rate, heart rate variability, skin conductance, and facial electromyography, will be recorded before and after treatment during a three minute anxiety probe specific to the patients index trauma. These measures will be compared to patients self reported subjective accounts of symptom improvement on traditional measures of PTSD pathology Subjective Units of Distress SUDs, PTSD Checklist-Military Version PCL, Clinician Administered PTSD Scale CAPS, and the Beck Depression Inventory BDI. This goal is significant for veterans because currently no widely used objective criteria exist to measure treatment progress in PTSD. While the preponderance of existing evidence suggests that no one objective psychophysiological measurement will be a valid correlate for all individuals, even establishing a measurement paradigm that can show mean differences between groups will provide researchers with an objective tool to measure outcomes on clinical trials. 