The Bispectral Index (BIS) is a single numeric value that indicates the depth of hypnosis by estimating the level of electrical activity in the brain through analysis of the frequency bands in the electroencephalogram. The BIS was primarily developed to monitor the level of hypnosis during surgery and has recently begun to be used in critically-ill patients. Currently, there is little experience of the BIS in critically-ill children. We present 6 cases that illustrate the utility of BIS monitoring in the PICU. We assessed sedation and analgesia during mechanical ventilation with and without neuromuscular block in two patients, and the effect of anesthetic agents during a surgical procedure in the PICU. The BIS was also useful in the continuous monitoring of the level of consciousness in a patient with encephalitis and in the early detection of brain death. Pacer-induced artefacts in the BIS value are also described. We conclude that BIS monitoring may be a useful, noninvasive method for assessing the level of hypnosis in critically-ill children.