Objective: To examine the validity of a neurobehavioral inventory for adults with traumatic brain injury. Design: Construct validity was examined by applying principal components and confirmatory factor analytic procedures. Internal consistency of factors was examined using Cronbach's alpha. Criterion-related validity was examined by comparing inventory scale scores with neuropsychological and personality test variables. Setting: Medical center outpatient clinic. Participants: 520 consecutive adult patients with traumatic brain injury were administered psychological and neuropsychological tests; 520 informants, primarily family members, completed the neurobehavioral inventory. Main Outcome Measure: Neurobehavioral inventory with items describing symptoms and daily living problems; scale scores were compared with a set of neuropsychological measures and Minnesota Multiphasic Personality Inventory scores. Results: Principal components and confirmatory factor analytic procedures identified six scales with a total of 70 items. The primary scale inclusion criterion required a minimum factor loading of .40. Chronbach's alpha analysis revealed acceptably high internal reliability for all scales ranging from .86 to .95. Scale scores were statistically compared with patients' scores on neuropsychological and personality tests. Poor neuropsychological test performance and greater levels of psychopathology were associated with greater frequency of perceived neurobehavioral problems. Conclusions: Findings suggest that the neurobehavioral inventory is a promising means of investigating informants' perceptions of outpatients' everyday problems. Such information can serve as a complement to historical information, test results, and information from standardized interviews to develop a holistic perspective of patients. Differential weighting of items, association of scales with other measures, and validation with other neurological patient populations are recommended avenues for future research.