This article describes the development and characteristics of the database that supports the research and demonstration aspects of the traumatic brain injury (TBI) model systems project sponsored by the National Institute on Disability and Rehabilitation Research. Criteria for inclusion of patients in the database were external force causing damage to brain tissue, 16 years of age or older, and admitted alive to a designated model system hospital emergency department within 8 hours of injury. Patients admitted to model system acute care but not rehabilitation (Level I) were sampled; those completing rehabilitation (Level II) were monitored using full protocol. Both had ongoing annual follow-up. Variables in the dataset were patient demography, cause of injury, specific diagnosis (including impairment and disability), certain interventions, costs, and outcomes relating to disability and handicap. In addition to Glasgow Coma Scale and Revised Trauma Scores, data collection instruments included a neuropsychological test battery, functional assessment measures, Disability Rating Scale, Rancho Los Amigos Scale, and the Community Integration Questionnaire.