After initial loss of consciousness following brain injury, background EEG may show slowing and posterior slow waves are observed, consistent with the existence of commotio cerebri, particularly in children. However, discrepancies between cerebral electrogenesis and the clinical condition may also persist for several weeks. As EEG is correlated with the stage of posttraumatic coma, its reactivity to stimuli is of value. While important EEG impairment with paroxysmal abnormalities is frequent in children, the patients' outcome is poorly correlated with initial EEG record. In intensive care units, the use of continuous digitized EEG techniques has opened new avenues. Though in case of mild risks, EEG and clinical follow-up may be sufficient after brain injury, EEG recording is recommended when computerized tomography (CT-scan) is normal in case of severe risks. When consciousness impairment is unexplained by the importance of the brain injury, emergency CT-scan is recommended, searching for intracranial hematoma. If CT-scan proves to be normal EEG should then be recorded, searching for local injury. EEG may uncover non-convulsive status epilepticus, mainly in elderly patients. In case of early seizures, EEG recording should be done within the first 24 hours following brain injury. In the post-ictal period, EEG should be recorded in emergency in case of confusional state lasting more than 30 minutes, as potential non-convulsive status epilepticus should not be underestimated. EEG is not of good predictive value for posttraumatic epilepsy; however, the existence of paroxysmal, local abnormalities is a risk factor. Recording of abnormalities may be useful for the medico-legal expert.