Traumatic brain injury is the leading cause of death and disability among young adults. Clinical evaluation is of limited value in the assessment of patients with traumatic brain injury and is often inaccurate in determining the extent of brain damage. Neurophysiological techniques and neuroimaging can provide valuable prognostic information and are useful in monitoring for seizures and other causes of secondary brain damage and in tracking the effects of therapy. More recently, cognitive electrophysiology and functional magnetic resonance imaging have shown that many patients clinically deemed to be in vegetative or in minimally conscious states are, in fact, aware. This opens new frontiers for further research into establishing communication with otherwise unresponsive patients.