Intravenous sedation during dental treatment is primarily used in outpatient clinics. Maintenance of a level of sedation sufficient to allow treatment while using the minimum dose possible and to induce faster waking is very important. The benefits of bispectral index monitoring have recently been reported for many applications, and it is expected to prove useful in intravenous sedation during dental treatment. However, because the sensor is attached to the forehead, which may be close to the site of operation, and because no neuromuscular blocking drugs are used, monitoring may be excessively interrupted by artifacts such as electromyographic input. Thus, we investigated the usefulness of bispectral index monitoring for patients under intravenous sedation during dental treatment. The incidence of "good" electroencephalograms, for which the electromyogram was less than 50 dB, signal quality index was more than 25%, and impedance was less than 10 kOhms, was 82.4% +/- 9.2%. These findings suggest that bispectral index monitoring will prove effective for intravenous sedation during dental treatment.