Traumatic brain injury (TBI), defined in the medical literature as a disruption in brain function that is caused by a head injury, has become known as one of the "signature wounds" of the wars in Iraq and Afghanistan due to its high occurrence in post-deployment service members and veterans of these wars. As service members return home, many need ongoing care for mild, moderate, or severe TBI. The growing number of TBI patients and the nature of their injuries creates the need for increased treatment capacity for veterans, and raises a number of policy issues that Congress may move to consider. This book provides a review of traumatic brain injury (TBI) as an illness, its prevalence among veterans, current activity to address the issue in the Department of Veterans Affairs, and current policy issues.