The Neurobehavioral Assessment Scale (NAS) was developed to measure the full range of behavioral functioning from fully alert to deep coma. This investigator-rated scale was evaluated in 60 patients undergoing conscious sedation for maxillofacial procedures. The results obtained on the NAS were reliable, as evidenced by high correlations between the ratings of the two raters. The scale is also valid as determined by high correlations between the NAS and a standard scale, the Glasgow Coma Scale (criterion validity) and between the NAS and the Digit Symbol Substitution Test (behavioral validity). The NAS clearly distinguished between two levels of sedation (heavy and light). Furthermore, the NAS appears to be better able to discriminate among the different degrees of sedation in lightly sedated patients than the Glasgow Coma Scale.