S100B protein (S100) is a constitutive protein of glial cells, whose physiological functions are both intracellular, i.e. intracytosolic calcium binding, and extracellular, e.g. by promoting neuritic proliferation and/or neuronal apoptosis. Due to specificity of its cellular expression, S100B protein is a useful biological marker of acute neurological disorders, such as ischemic or haemorrhagic stroke, and traumatic head injury. hemorrhage, ischemic stroke) or traumatic (TCC). Plasma S100 is significantly increased in subjects with a major TCC, but also in the majority of minor or moderate TBI. A prognostic value of S100 also was suggested : patients who exhibited medical or social sequelae after several months after TBI also shoed high plasma levels of S100 in the first hours of the head injury. Such results of international clinical studies proposed S100 as a biomarker of diffuse brain injury, and indicate the importance of early determination of plasma concentration of S100 and its integration among the other elements of diagnosis (imaging) for assessing the severity of trauma and its short and long terms.