The Trauma Symptom Inventory (TSI) is one of the most widely used instruments in the assessment of PTSD related symptoms [Elhai, J.D., Gray, M.J., Kashdan, T.B., Franklin, L.C., 2005a. Which instruments are most commonly used to assess traumatic event exposure and posttraumatic effects? A survey of traumatic stress professionals. Journal of Traumatic Stress 18, 541-545]. In spite of the fact that the TSI has demonstrated adequate psychometric qualities in past studies [Briere, J., 1995. Trauma Symptom Inventory professional manual. Psychological Assessment Resources, Psychological Assessment Resources; Briere, J., Elliott, D.M., Harris, K., Cotman, A., 1995. Trauma Symptom Inventory: Psychometrics and association with childhood and adult victimization in clinical samples. Journal of Interpersonal Violence 10, 387-401; McDevitt-Murphy, M.E., Weathers, F.W., Adkins, J.W., 2005. The use of the trauma symptom inventory in the assessment of PTSD symptoms. Journal of Traumatic Stress 18, 63-67] the measure's psychometrics have only as of yet been examined among civilians. We examined the TSI's psychometric properties using archival data from 221 treatment-seeking veterans evaluated for military-related posttraumatic stress disorder (PTSD) symptoms. Results demonstrated adequate internal consistency for the TSI's clinical scales (alphas ranging from 0.73 to 0.91). Convergent validity was established for clinical scales tapping PTSD's re-experiencing, avoidance and hyperarousal symptoms, and depression and irritability, against other similar measures. Structural validity was also supported in confirmatory factor analyses, with a three-factor model, and a similar model merging two of these three factors, best fitting the observed data.