This study examined the ability of early measures of traumatic brain injury (TBI) severity to predict neurobehavioral and functional skill outcomes shortly after injury and at 1 year postinjury. Ninety-eight children aged 6 to 15 years with TBI were consecutively identified on presentation to two regional medical centers. Ten measures of TBI severity were subsequently administered: initial Glasgow Coma Scale (motor, eye, verbal, and total GCS), duration of loss of consciousness, Abbreviated Injury Scale Head score, GCS motor score at 3 days postinjury, days to reach a total GCS score of 15, days to reach a GCS motor score of six, and duration of posttraumatic amnesia (days to reach a 75% performance on the Children's Orientation and Amnesia Test [COAT]). Cases were matched individually with controls on the basis of age, gender, school grade, the classroom teacher's assessment of pre-morbid level of academic performance in reading and arithmetic, and pre-morbid behavior. Both groups received intellectual, neuropsychologic, academic, and functional skill assessments three weeks after the case achieved full orientation and 1 year later. The indices of injury severity that were most predictive of both early and 1-year outcome across all neurobehavioral and functional measures were (1) days to an age-adjusted 75% performance on the COAT, (2) days to a GCS score of 15, and (3) initial total GCS score. For most outcome areas, a single measure of severity predicted outcome almost as well as multiple measures. However, early and 1-year academic performance and 1-year memory performance were best predicted by considering multiple indices of brain injury severity. The GCS verbal and motor scores were better predictors of outcome than the GCS eye score. However, consideration of individual GCS subscores did not improve upon prediction of outcome versus the GCS total score. These results provide strong validation for the use of duration of posttraumatic amnesia, measured by the COAT, as a measure of TBI severity and a significant indicator of neurobehavioral and functional outcome in children.