The Traumatic Brain Injury (TBI) Model Systems Program has been funded by the National Institute on Disability and Rehabilitation Research (NIDRR) since 1987. Until recently, this program has consisted of four centers that conducted priority-focused research on specific aspects of TBI and analyzed data on the basis of a uniform, comprehensive national database. In 1997, $5 million in additional funding was allocated for the expansion of this program. In October 1998, after a competitive renewal process, a total of 12 new centers were awarded, bringing the total TBI Model Systems to 17. In addition to the creation of new centers, funding was provided for specific collaborative research projects and increased resources for the TBI National Data Center. Below are the abstracts for both the newly funded systems and the existing systems.