Objective: To investigate improvement rates and medical services costs in older brain injured adults relative to younger patients. Design: Descriptive statistics were computed in a prospective comparative study of 50 patients 55 years and older and 50 patients 18 to 54 years old matched for gender and injury severity (number of days in coma, admission Glasgow Coma Score, intracranial pressure). Independent t tests were performed to examine differences between the two samples on specific variables. Selling: Five medical centers in the federally sponsored Traumatic Brain Injury Model Systems Project that provide emergency medical services, intensive and acute medical care, inpatient rehabilitation, and a spectrum of community rehabilitation services. Participants: Patients were selected from a national database of 531 rehabilitation inpatients admitted to acute care within 8 hours of traumatic brain injury between 1989 and 1994. Main Outcome Measures: Disability Rating Scale, Functional Independence Measure, Rancho Los Amigos Levels of Cognitive Functioning Scale, length of stay, acute care and rehabilitation charges, and discharge disposition. Results: Older persons averaged a significantly longer rehabilitation length of stay, higher total rehabilitation charges, and a lower rate of change on functional measures. No significant differences between groups were found for acute care length of stay, daily rehabilitation charges, acute care charges (daily or total), or discharge disposition. Conclusions: Although older persons demonstrated functional changes, the cost of change was substantially higher than for younger patients, coincident with longer lengths of stay. These higher overall charges and slower rates of change may effect changes in referral and management patterns.