Monitoring the metabolism and function of the central nervous system not only is an old idea but also is a topic that is of increasing interest to the technological evolution. Beside the optimization of cerebral and spinal cord perfusion and the preservation of vasoreactivity to ensure the viability of cerebral tissues and structures, we want to know more and more about the real intimate situation of these organs in real time at the patient’s bedside. To this end, several tracks have been explored during the two last decades, leading to the development of numerous concepts and the conception of various monitoring systems. One of the main problems is to characterize the respective strong points and weaknesses of those ones and to conclude regarding their individual relevance and value in current clinical practice. It is more and more clear that the combination of different categories of monitoring is a way to try to find the most valuable technological compromise, to increase the chance of prediction or of early detection of intercurrent deleterious events corresponding to the concept of multimodality. The intraoperative period and the intensive care goals and targets are appreciably different. This is the reason for the attempt to define different and distinct sets of goals and targets for the intraoperative anesthetic setting and for the intensive care unit.