BACKGROUND: The aim of this study was to evaluate whether continuous infusion of remifentanil during propofol anesthesia could produce opioid-induced hyperalgesia (OIH) and whether an intravenous bolus of fentanyl could control OIH in the management of postoperative pain. METHODS: One hundred fifty-nine women undergoing gynecologic surgery were randomly divided into four groups. Group C: nitrous oxide and propofol infusion (3-4 microg/ml, n = 40), Group F: propofol infusion and intravenous bolus administration of fentanyl (1 microg/kg) after suturing the peritoneum (n = 40), Group R: propofol and remifentanil infusion (2-4 ng/ml, n = 40) and Group RF: propofol, remifentanil infusion and intravenous bolus administration of fentanyl (n = 39). Patient controlled analgesia was started after the operation. The postoperative visual analog scale (VAS) was measured in the recovery room, then at 2 h, 6 h, 12 h, and 24 h after the operation. RESULTS: The VAS scores for Groups R and F in the recovery room were lower than for group C (P < 0.05), but there were no differences 2 h after the operation. The VAS scores for Group RF 6 h and 12 h after the operation were higher than those for group C (P < 0.05). CONCLUSIONS: Our results suggest that low dose (2-4 ng/ml) continuous infusion of remifentanil during propofol anesthesia does not produce marked hyperalgesia. However, an intravenous bolus of fentanyl can aggravate OIH induced by remifentanil.