OBJECTIVE The purpose of this study was to determine whether the bispectral index scale (BIS) would provide added benefit to established methods of monitoring conscious sedation with midazolam (M group) or midazolam supplemented with ketamine (MK group). METHODS BIS was prospectively and blindly examined in 22 patients receiving outpatient oral surgery with conscious sedation supplemented with local anesthesia. RESULTS The average midazolam dose in the midazolam group over the treatment period was 0.01 mg/kg/h, and the average midazolam plus ketamine dose was 0.01 and 0.05 mg/kg/h, respectively. Mean BIS values throughout the sedation study period were 90 for the midazolam group and 94 for the midazolam plus ketamine group. The addition of ketamine did not lower BIS. BIS values did not alter significantly over time except for an expected transient drop after the midazolam bolus induction. CONCLUSIONS BIS levels remained close to baseline levels, suggesting that BIS would not provided any additional benefit to currently established methods of monitoring patient consciousness during conscious sedation for oral surgery.