Traumatic brain injury is the most common cause of death and disability in young people, with an annual financial burden of over $50 billion per year in the United States. Traumatic brain injury is defined by both the initial primary injury and the subsequent secondary injuries. Fundamental to emergency department management is ensuring brain perfusion, oxygenation, and preventing even brief or transient episodes of hypotension, hypoxia, and hypocapnia. Cerebral perfusion pressure is a function of intracranial pressure and systemic blood pressure, and it must be monitored and maintained. Current research is devoted towards the prevention and treatment of secondary injury. The emergency clinician must be vigilant in maintaining homeostasis while coordinating the downstream care of the patient, including the intensive care unit and/or the operating room.