Depth of anesthesia monitors are increasingly used in clinical anesthesia practice. Bispectral Index (BIS) and M-Entropy are examples to these devices, both of which are available at our institution. Both BIS and M-Entropy use a unilateral, single channel of EEG to derive a number indicating the anesthetic depth. These devices have similar disposable skin probes that can be applied on either side of the forehead. Since the depth of anesthesia for an individual is the same over the whole brain cortex at a given point in time, BIS numbers obtained over the left and right side of the forehead should agree. The same should be true for M-Entropy as well.