Background and objectives: This study was designed to quantify the additional postoperative analgesic efficacy of a single dose of ketoprofen in patients undergoing thyroid surgery using two different intraoperative analgesic regimens. Methods: One hundred and twenty patients were randomly assigned to one of four groups: intraoperative fentanyl or remifentanil with or without ketoprofen (n = 30 for each group). Intravenous ketoprofen (1.5 mg kg−1) or saline was administered 45 min before the end of surgery. Pain scores, opioid demand and length of stay in the postanaesthesia care unit were assessed in a blinded manner. Results: Patients receiving intraoperative fentanyl with saline had significantly lower visual analogue scale pain scores in the postanaesthesia care unit compared with those receiving intraoperative remifentanil with saline (55 ± 10 mm vs. 80 ± 18 mm, P < 0.05) and they stayed shorter in the postanaesthesia care unit (86 ± 24 min vs. 126 ± 37 min). In conjunction with intraoperative fentanyl, ketoprofen significantly decreased postoperative pain scores (40 ± 10 mm, P < 0.05 compared with fentanyl alone) and opioid demand (4 of 30 patients vs. 14 of 30 patients compared with fentanyl alone, P < 0.05). Patients receiving intraoperative remifentanil had no additional analgesic benefit with ketoprofen. Conclusion: After thyroid surgery, patients receiving intraoperative fentanyl had lower pain scores and needed less rescue analgesia compared with patients receiving intraoperative remifentanil. The adjunction of ketoprofen further improved analgesia in patients who received intraoperative fentanyl only.