Objectives : Posttraumatic stress disorder (PTSD) is classified as an anxiety disorder. PTSD occurrence is known to be increased in middle-aged and older people, female, and individuals with a previous history of psychiatric disorders, lower education levels, low socioeconomic status, and severely injured patients. Anxiety symptoms are also related to later development of PTSD. In this study, we investigate the influences of injury severity and sociodemographic factors on severe anxiety in PTSD patients with no previous history of psychiatric disorders. Methods : Forty-one PTSD patients without previous history of psychiatric disorders were recruited from the psychiatric clinic at Chosun University Hospital. Subjects underwent psychiatric and physical examinations including the Injury Severity Score (ISS), Beck Anxiety Inventory (BAI), and Korean-Wechsler Adult Intelligence Scale (K-WAIS). We defined severe anxiety as a BAI scores of 30 or more. Logistic regression analyses and multi-step model selection were applied to identify predictive factors for severe anxiety. Results : In univariate analysis, age, ISS, and socioeconomic status were found to be significant factors. Through multivariate logistic regression analyses and a stepwise model selection, we found the combination of age and ISS to be the best-fitted model for affecting severe anxiety in PTSD patients without a previous history of psychiatric disorders. Conclusion : Our findings suggest that the combination of age and ISS could develop severe anxiety in PTSD patients with no previous history of psychiatric disorders.