Methods: 50 patients ASA class I or II aged 18-75 years undergoing ambulatory elective surgery will be randomized to one of two groups: those who receive propofol + saline (control group: n = 25) or propofol + remifentanil (propofol-remifentanil group: n=25). We will use target-controled infusions (Alaris®PK) for both drugs: propofol (Marsh et al.´s pharmacokinetic model) and remifentanil (Minto et al.´s pharmacokinetic model). The patients wil be premedicated with midazolam 1 mg iv before surgery. The target concentration for each patient was determined using the Dixon´s up-and-down method. Predetermined propofol and remifentanil blood and effect site concentrations were held constant for at least 10 min. After equilibration of plasma and effect site propofol concentrations, the SLMA will be inserted, and secured according to the manufacture´s recommendations, without the use of muscle relaxants. In control group, propofol concentrations will start at 4 μg ml-1, with 0,5 μg ml-1 as the step size, with the coadministration of saline. In propofol-remifentanil group, propofol + remifentanil at a target-controlled infusion 5 ng/mL will be coadministered. A single measurement will be obtained from each patient. If the patient reacted with movement, the propofol concentration for the next patient was increased by 0.5 μg ml-1 ±1 ; if there was no movement, it was decreased by 0.5 μg ml-1 ±1 . Movement was defined as bucking or gross purposeful muscular movement within 1 min of LMA insertion. Values of Cp 50 wil be determined by calculating the midpoint concentration after at least seven crossover points (movement/non movement) will be obtained in each group.