Objectives: To understand the course of changes in function and need for assistance in the chronic stages of TBI; and to identify factors associated with these changes. Design: Longitudinal review of participants in the TBI Model Systems Database, who have been prospectively followed for at least 10 years. Participants: Four hundred and seventy-eight individuals with TBI that occurred between 25 October 1988 and 31 December 1998, enrolled in the TBI Model Systems National Database, eligible for 10-year follow-up when data was extracted, with completed data collection at either year 1 or 2 and year 10. Results: Significant between age group differences were found for FIM toileting, bladder, bowel, toilet transfers, locomotion, problem-solving and memory; SRS; DRS level of functioning, employability and total; and GOS. With regard to functional independence, there were significant differences by age category for all FIM components except memory. Significant differences were noted for age category and level of dependence as measured by the DRS (LOF 1.55) and GOS (GOS 24). Supervision needs significantly increased as a function of age. Significant differences were found for diminished function over time. Significant differences were noted for residence at 10 years post-injury. Conclusions: For those individuals that survive to 10 years post-TBI, age is a major factor in requiring assistance of another person for supervision as well as assistance in basic self-care, continence and mobility. © 2012 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.