Objective: Determine the prevalence of secondary adrenal failure, and other factors related to secondary adrenal failure in patients with traumatic brain injury after 06 months period Methods: crosssectional description. Implementation period from 04/2011- 04/2012 at the Department of Neurosurgery Care Unit and Outpatient Department - Cho Ray Hospital. Traumatic brain injury patients with Glasgow at admission 13 points and brain damage on CT scan were evaluated the function of pituitary-adrenal axis after 06 months. Pituitary - adrenal axis failure was defined as synacthene 250mcg test: blood cortisol 30 minutes after injection ACTH 200 ng/ml combination with low ACTH or normal range. Results: 156 patients in the 06-month follow-up, 53 died patients accounted for 33.9 percent. 88 survived patients returned for study, males accounted for 89.8 percent. Average age of patients was 31.1 percent 13.7 (minimum age 15, maximum 71). 73 percent of patients with Glasgow at admission 9 points Mean time for reexamination after traumatic brain injury: 5.8 percent 1.1 months. There are seven patients with secondary adrenal failure, accounting for 8 percent. Frequency of secondary adrenal failure in Glasgow group 9 points higher than the Glasgow group 9-13 (9.4 percent vs. 4.2 percent). No factors significantly associated with secondary adrenal failure. However, all seven patients with secondary adrenal failure were severe disability and sequelae were male patients. Cut off point of cortisol level in secondary adrenal failure diagnosis was 93.5 ng/ml with a sensitivity and specificity of 71.4 percent and 75.3 percent respectively. The area under the curve was 0.704. Conclusion: The prevalence of secondaryadrenal failure in the period of 06 months after traumatic brain injury was 8 percent. Frequency of secondary adrenal failure in Glasgow group 9 points higher than the Glasgow group 9-13. No factors significantly associated with secondary adrenal failure. All 7 patients with secondary adrenal failure were severe disability and sequelae were male patients.