Background. Although initial studies of preemptive analgesia showed that preoperative blockade with local anaesthetics or preoperative administration of systemic opioids was more effective in reducing postoperative pain than control conditions involving no treatment, the result of subsequent investigations comparing the effects of preoperative treatment with the same treatment initiated after surgery have produced inconsistent results. The reasons for the lack of consistency are not clear. Studies about the relationship of preemptive analgesia and both analgesic consumption and surgical stress response are limited. The purpose of this study was to evaluate the effect of preemptive intravenous morphine on both postoperative analgesic consumption and surgical stress response.