Both prehospital and hospital management of patients with severe head injury has clearly improved in the last decades. There is a greater knowledge of how secondary brain injury is caused and how it can be prevented. Intracranial mechanisms (e.g. haematoma and elevated intracranial pressure and systemic mechanism (e.g. shock and hypoxaemia) are two of the major causes of secondary brain injury. Adequate prehospital evaluation and treatment determine the later outcome for the patient. The Glasgow Coma Scale has become the standard score for assessing the level of consciousness. Early prehospital treatment must prevent secondary brain damage through adequate oxygenation (intubation, ventilation) and a sufficient cerebral perfusion pressure (treatment of shock). The neck of the patient should be positioned straight and the upper part of the body should be elevated to about 30 degrees. The prophylactic use of steroids, mannitol or high dose barbiturates is not indicated. Aggressive hyperventilation (pCO2 < 30 mmHg), especially during the first few days after severe brain injury, should be avoided.