The discovery of anaesthesia transformed the human condition, and unplanned awareness returns a patient to the nightmare that was surgery before anaesthesia and effective analgesia. Significant advances in the pharmacology and technology of anaesthesia have still not brought reliable means of monitoring its depth much closer, although because awareness is such a serious complication, considerable research effort has been dedicated to the search for methods of detection. Some of these remain research tools or are not yet in widespread use, but you should have some idea about which of them may in due course find their way into clinical practice. Most current interest centres around bispectral index (BIS) monitoring, with recommendations both from the Association of Anaesthetists and from NICE, which are summarised in this section, and it is likely that the oral will focus more on BIS than on the other technologies.