Traumatic brain injury (TBI) is common and a major health and socioeconomic problem worldwide. In the United States it is estimated that someone suffers a TBI every 15 seconds and that >2% of the population lives with TBI-associated disability. TBI is a heterogeneous disease in cause, pathology, severity, clinical presentation and prognosis that may occur in isolation or be associated with other extracranial injuries. Despite much research and success in animal studies, effective drug therapies are missing in clinical trials [1–3]. Instead TBI management is centered on the early identification and removal of mass lesions and on the detection, prevention, and management of secondary brain insults such as hypotension, hypoxia, seizures, and elevated intracranial pressure (ICP), among others, that evolve over time following the primary injury. Hence management in the neurocritical care unit (NCCU) can have a significant impact on patient outcome. Much of this care has been codified in various guidelines published by organizations such as the National Institute for Health and Clinical Excellence in the United Kingdom or the Brain Trauma Foundation and Neurocritical Care Society in the United States [4–8]. In this chapter we will briefly review the classification, pathology, and pathophysiology of TBI, provide indications for surgical intervention, and discuss important aspects of critical care. Several topics, e.g. cerebral blood flow (CBF), ICP, monitoring, ventilation, sedation, and brain death, are also enlarged upon in other chapters in this book. We will concentrate on moderate and severe TBI in adults since it is these patients who usually require intensive care. The reader is referred elsewhere for recent reviews on concussion, mild TBI, and care of pediatric TBI [9–17].