Modern anesthesia aims at ensuring safe awakening from anesthesia with good pain control extending to the postoperative period. A good strategy to achieve this goal is to prevent rather than treat severe postoperative pain.This study was designed to evaluate the efficacy of intramuscular, intrathecal or epidural morphine as pre-emptive analgesia prior to skin incision. It also aimed at determining the same regimens as postoperative analgesia (with particular emphasis on the first request for analgesia), pain scores, histamine release, hemodynamics, side effects and/or complications in the first 24 hours postoperatively.This study demonstrated longer analgesia, better pain scores, less release of stress hormones and histamine in the first 24 hours postoperatively with intrathecal or epidural morphine, in addition to general anesthesia prior to skin incision, than intramuscular morphine in addition to general anesthesia before skin incision.