Traumatic brain injury is the main cause of death and disability in children and adults in Western Countries. The definitive brain injury is a consequence of pathophysiological mechanisms that begin at the moment of an accident and may extend for days or weeks. Traumatic brain injury may be classified as diffuse or focal. These two mechanisms are commonly associated in a patient, however one is generally predominant. Therefore knowledge of the pathophysiological mechanisms of brain injury in head trauma is important to establish the therapeutic, clinical and surgical measures. In this paper the authors present a critical review of the literature on the pathophysiological principles of traumatic brain injury.