Approximately one-half of vehicle occupants with traumatic brain injury (TBI) have a mild TBI (admission Glasgow Coma Scale (GCS) score of 13-15 with transient loss of consciousness). However, despite the label of "mild", many of these injuries result in long-term consequences; frequently these sequelae go unrecognized, as the patients are lost to medical follow-up. The Crash Injury Research Engineering Network (CIREN) project affords us the opportunity to examine the crash circumstances, injury sources and outcomes of mild TBI cases in greater detail.