The preliminary results of a multicenter study designed to determine the utility of the processed EEG in combination with heart rate and blood pressure for estimating anesthetic depth are reported. The study is planned to include 1,000 ASA I, II, and III patients undergoing surgery with at least a 60-minute duration of anesthesia. The preliminary results indicate that the use of EEG and clinical signs may provide better control of anesthetic depth. The study design provides ideal conditions for determining whether spectral edge frequency is a useful criterion for management of routine general anesthesia in a typical clinical environment.