Using a prospective, cohort design, we investigated whether children with mild traumatic brain injury (TBI) differed from individually matched controls on measures of intellectual, neuropsychological, academic, and "real world" functioning. Subjects included children between the ages of 6 and 15 years who sustained mild, moderate, and severe closed head injuries and were consecutively identified on presentation to the emergency departments of two regional, university medical centers. One hundred twenty-nine children were eligible for enrollment. Seventeen refused enrollment. Fifty-nine of the 112 enrolled children were classified as mildly injured. Six of these children dropped out, leaving 53 mildly injured cases for analysis. Individually matched controls from the classroom of the injured cases were identified based on age, gender, and premorbid academic achievement and behavior. Assessment measures included standardized intellectual, neuropsychological, and academic measures. Also, parent and teacher questionnaires, measuring social, educational, domestic, and community living skills were used. Among 51 outcome variables only five were significantly associated with injury at initial or 1-year testing after adjusting for multiple comparisons. However, these five associations were either very weak or implausible. Results from this study suggest that mild TBI produces virtually no clinically significant long-term deficits in intellectual, neuropsychological, academic, or "real world" functioning.