Many clinical and laboratory experiments have been developed to prevent or decrease post-operative pain. One of these methods is pre-operative administration of opioid. Recently there have been differing and debatable results reported of pre-operative treatment for post-operative pain management. It was our study to determine whether pre-operative epidural fentanyl prevented central facilitation or wind up of spinal cord from nociceptive afferent input through c-fibers. We evaluated the effect of epidural fentanyl 50 mcg 10 minutes before operation and 10 minutes before the end of surgery. 28 parturient women for Cesarean Section were randomly allocated to receive the epidural fentanyl either at 10 minutes before operation (Group 1, n=14) or 10 minutes before the end of surgery (Group 2, n=14). All of the 28 parturient women were anesthetized with epidural block using (22 ml of) 2% lidocaine supplemented with light general anesthesia ($N_2O$ 2 L/min-$O_2$, 2 L/min), we controlled post-operative pain with epidural PCA(patient controlled analgesia) infusion of meperidine and 0.07% bupivacaine. The action duration of epidural fentanyl from the end of surgery to the first requirement of analgesics with epidural PCA were not significantly different between the two groups. No significant differences between two groups were observed in VAS pain score at 1, 2, 3, 6, 12, 24, and 48 hours after the operation. The number of self administration of narcotics with PCA during 48 hours after surgery were the same between the two groups. The hourly infusion rates of demerol were the same. Pre-operative administration of fentanyl was not clinically effective compared to administration just before the end of surgery for postoperative pain control.