To describe the current status of the Traumatic Brain Injury Model Systems (TBIMS) National Data Base and present major descriptive findings based on the original research and demonstration issues for which the database was developed, and to describe patient outcomes at discharge from inpatient rehabilitation and at 1 year post injury Design: Prospective, longitudinal multicenter study. Setting: TBIMS located at the Medical College of Virginia, Richmond, Va; Wayne State University/Rehabilitation Institute of Michigan, Detroit, Mich; The Institute for Rehabilitation and Research, Houston, Tex; and Santa Clara Valley Medical Center, San Jose, Calif. Data Set: Demographic, diagnostic, treatment, and outcome data on 660 individuals consecutively discharged from the four TBIMS between March 1989 and September 1995. Results: TBIMS individuals are typically in their mid-30s, male (77%), and white (51%); have a high school education or less (71%); and are as likely as not to be employed at the time of injury (50%). Vehicle-related injuries are the leading cause of injury (56%). Individuals tend to suffer moderate to severe brain injuries, with 77% experiencing loss of consciousness and 98% experiencing. posttraumatic amnesia. The average combined length of stay for acute care and inpatient rehabilitation decreased approximately 25%, from 83 days in 1989 in 63 days in 1994. The Functional Independence Measure scores indicated overall functional improvement from an average level of requiring ''Moderate Assistance'' at the time of rehabilitation admission to an average level between ''Moderate Independence'' and ''Complete Independence'' at 1 year post injury. As indicated by the Community Integration Questionnaire, individuals tended to do best in the social aspects of community integration and worst in productivity. Conclusion: This article addresses the original research and demonstration issues posed by the creators of the TBIMS National Data Base. It describes the TBIMS population and presents outcomes at rehabilitation discharge acid at 1 year post injury. This information provides a benchmark for future study.