Objective: To assess the usefulness and validity of a brief personality assessment for orthopaedic trauma patients. Methods: The NEO-Five Factor Inventory was evaluated within the context of the Lower Extremity Assessment Project, a prospective study of patients with severe lower extremity trauma admitted to eight level I trauma centers. Patients/Participants: The NEO-FFI was administered to 557 adults and 416 of their significant others. At 2 years postinjury, the NEO-FFI was readministered to 396 patients. Main Outcome Measures: Main outcome measures were as follows: (a) agreement between patient and significant other scores; (b) stability of personality traits over two years; and (c) the relationship of the measured NEO-FFI traits with patient characteristics and health habits. Results: There was fair to moderate agreement between assessments of personality provided by the patients themselves and their significant others, with intraclass correlation coefficients ranging from 0.44 to 0.54 for the different domains of personality. Patient assessments on the NEO-FFI were found to be robust with no significant changes in four of the five personality domains at 2 years postinjury. We also found that personality traits of patients are related to patient characteristics and behaviors in the directions that were expected. Conclusions: The NEO-FFI is a brief, valid, and stable measure of underlying personality traits that is practical for use in a trauma setting. Its use in both outcomes research and patient evaluation should be encouraged. In cases in which patients cannot complete the test, evaluations by significant others may be useful.