The Glasgow Coma Scale has been used since 1974 to assess the severity of brain damage, and thus as a tool to predict mortality and compare results between series of patients. Variables such as age, secondary brain insults, and type of cranial lesion seen on computed tomography scan are closely related with outcome. The authors discuss the limitations of the Glasgow Coma Scale and how general intensive care severity scoring systems used in critical care perform very well in assessment of severity of brain damage, with good discrimination and calibration. Other systems also perform very well, but they are not widely used. Moreover, other aspects of patients with head trauma, such as genetic predisposition, inflammatory response to injury, and management could play a role in predicting mortality. To predict mortality accurately in head trauma patients, physicians need a system that includes all the important variables, that is easy to perform at admission, and that has wide acceptance. In patients with subarachnoid hemorrhage, a reliable neurologic evaluation and a careful cranial computed tomography interpretation are enough to assess the outcome.