Fatigue is frequent and disabling in patients with traumatic brain injury (TBI). Its mechanisms are complex and multifactorial. We performed a literature review of reports of the condition using the following key words: brain injury, depression, neuroendocrine dysfunction, and treatment. Five scales have been used to evaluate fatigue in TBI patients: the Fatigue Severity Scale, the visual analog scale (VAS) for fatigue, the Fatigue Impact Scale, the Barrow Neurological Institute (BNI) Fatigue Scale and the Cause of Fatigue (COF) Questionnaire. The BNI Fatigue Scale and the COF Questionnaire have been designed specifically for brain-injured patients. Fatigue is present in 43-73% of patients and is one of the first symptoms for 7% of them. Fatigue does not seem to be significantly related to injury severity not to time since injury. It can be related to mental effort necessary to overcome attention deficit and slowed processing ("coping hypothesis"). It can also be related to sleeping disorders and depression, although the relation between fatigue and depression are debated. Finally, fatigue can also be related to infraclinical pituitary insufficiency (growth hormone insufficiency, hypocorticism). To date, no published study of treatment of fatigue after TBI exists.