 Brain injury from explosive blast is a prominent feature of contemporary combat. Although protective armor and effective acute medical intervention allows soldiers to survive blast events, a growing number of veterans will have disability stemming from blast-related neural damage. Soldiers also return from combat with psychological disabilities caused by traumatic war events. The clinical presentation of individuals with blast-related neural damage and post-traumatic psychopathology are markedly similar and thus a clear description of the direct consequences of explosive blast is complicated by the emotional and cognitive sequelae of psychological trauma. We will use sophisticated measures of neural function and structure to characterize brain injury from explosive blasts in a sample of Operation Iraqi Freedom OIF National Guard soldiers who returned from deployment in the fall of 2007. Survey data gathered near the end of deployment indicated that over 50 of the brigade had been exposed to direct physical effects of explosive blasts. To fully characterize the effects of blast on the brain and differentiate them from post-traumatic stress disorder, we will contrast groups of soldiers exposed to blast and with groups experiencing post-traumatic stress disorder. This investigation will improve the characterization of blast-related traumatic brain injury, describe the essential features of the condition in terms of neural function and structure to inform diagnosis, and characterize mechanisms of recovery after blast-related neural injury to allow the creation of interventions that return soldiers to maximum levels of functioning. 