The 2023 Washington State Legislature directed the Washington State Institute for Public Policy to assess the potential need for developing specialized long-term care services and supports for adults with traumatic brain injuries (TBI) in the state. TBI is an acute event resulting from an impact to the head causing bruising and other damage to the brain. Health outcomes related to TBI can be chronic and introduce a need for long-term support services including rehabilitative care in hospital, transitional, and community- and home-based settings. Duration of healthcare use resulting from TBI depends on severity and comorbidities. To fulfill the legislatively mandated assignment the proposed study will describe the demographic and geographic distribution of TBI, TBI sequelae and comorbidities, and resources and facilities involved in the treatment of and rehabilitation from TBI among adults in Washington. We will examine if the incidence of TBI and use of rehabilitation services differ across demographic characteristics, geographic region, and payer type. This work will inform state legislators and groups working with the TBI-affected community about the prevalence of TBI and access to relevant health care services, with the purpose to support the appropriate provision of specialized care services and long-term supports for adults with TBI.