The Bispectral Index (BIS) is an empirically calibrated number derived from adult electroencephalograph data that correlates with the depth of sedation in adults. We tested the hypothesis that the BIS score is a valid measure of the depth of pediatric sedation in a study designed to avoid limitations of a previously published report. BIS values from 96 healthy ASA physical status I-II children aged 1-12 yr undergoing sedation were continually recorded and electronically transferred to a computer. Two independent observers blinded as to BIS score evaluated sedation using the Observer's Assessment of Alertness/Sedation (OAA/S) and the University of Michigan Sedation Scale (UMSS) at 3-5 min intervals. There was a significant correlation between BIS and UMSS and between BIS and OAA/S by both the Spearman's rank correlation test and by prediction probability (P < 0.001). In children <6 yr, there was a significant correlation between BIS and the clinical sedation scores for subgroups undergoing invasive and noninvasive procedures (P < 0.001). There was also good agreement between the 2 independent observers who assessed clinical sedation scores (kappa = 0.51, P < 0.001). We conclude that the BIS monitor is a quantitative, nondisruptive and easy to use depth of sedation monitor in children.