The Glasgow Outcome Scale (GOS) and its most recent revision, the GOS-Extended (GOS-E), provide the gold standard for measuring traumatic brain injury (TBI) outcome. The GOS-E exhibits validity when used with adults and some adolescents, but validity with younger children is not established. Because the GOS-E lacks the developmental specificity necessary to evaluate children, toddlers, and infants, we modified the original version to create the GOS-E Pediatric Revision (GOS-E Peds), a developmentally appropriate structured interview, to classify younger patients. The criterion, predictive, and discriminant validity of the GOS-E Peds was measured in 159 subjects following TBI (mild: 36%; moderate: 12%; severe: 50%) at 3 and 6 months after injury. Participants were included from two studies completed at the Pediatric Neurotrauma Center at Children's Hospital of Pittsburgh. We assessed the relationship among GOS-E Peds, the GOS, and the Vineland Adaptive Behavior Scales as well as other standardized measures of functional, behavioral, intellectual, and neuropsychological outcome. Premorbid function was assessed 24-36 h after injury. The GOS-E Peds showed a strong correlation with the GOS at 3 and 6 month time points. Criterion-related validity was also indicated by GOS-E Peds' association with most measures at both time points and at injury severity levels. The 3 month GOS-E Peds was associated with the 6 month GOS-E Peds, everyday function, behavior, and most cognitive abilities. Discriminant validity is suggested by weak correlations between both 3 and 6 month GOS-E Peds and premorbid measures. The GOS-E Peds is sensitive to severity of injury and is associated with changes in TBI sequelae over time. This pediatric revision provides a valid outcome measure in infants, toddlers, children, and adolescents through age 16. Findings support using the GOS-E Peds as the primary outcome variable in pediatric clinical trials.