Several monitors are currently proposed to evaluate the depth of hypnosis. Among them, Bispectral Index (BIS) is a well known and widely used parameter derived from the patient's electroencephalograph (EEG). A closed-loop anesthesia system can be built using BIS as the control variable, a proportional-integral-differential control algorithm, a propofol and a remifentanil target-controlled infusion systems as the control actuators Preliminary results show that this system can be used during surgery.