Objective To develop new patient-reported outcome (PRO) measures to better understand feelings of loss in caregivers of individuals with traumatic brain injury (TBI). Design Cross-sectional survey study. Setting Three TBI Model Systems rehabilitation hospitals, an academic medical center, and a military medical treatment facility. Participants Caregivers (N=560) of civilians with TBI (n=344) or service members/veterans (SMVs) with TBI (n=216). Interventions Not applicable.