 The increase of Corrected QT QTc interval is associated with age. It is known that most inhalation anesthetics or intravenous anesthetics can influence the QTc. In addition, tracheal intubation during induction can stimulates sympathetic activity, which, as a results, prolong the QTc interval. Therefore, the aim of study is to find out the effect site concentration of remifentanil for preventing QTc interval prolongation during intubation under propofol-remifentanil anesthesia in elderly patients. 