Total intravenous anesthesia and the new parameter for administering the most recent drugs, target-controlled infusion, as well as the introduction of new short half-life molecules that do not accumulate have made anesthesia in day surgery safer. In this study, the use of auditory-evoked potentials monitoring made it possible to determine the target plasma concentration of propofol that induces a narcosis sufficiently deep and strictly necessary for effectiveness, thus minimizing the anesthesiologic risk linked to the use and the dosing of the drug, reducing the hospitalization time, and decreasing the side effects for patients undergoing day surgery mammoplasty.