Purpose: To compare the analgesic efficacy and side effects of tramadol vs tra Methods: Randomised, double-blind study. Thirty-four patients undergoing elective colorectal or head and neck surgery were allocated to Group 1 (n = 18, PCA bolus 10 mg tramadol) or Group 2 (n = 16, PCA bolus 10 mg tramadol + 0.1 mg droperidol), Anaesthesia was induced with fentanyl and thiopentone and maintained with O-2, N2O plus enflurane or isoflurane with iv morphine at doses decided by the attending anaesthetists, Muscle relaxation was achieved with atracurium or vecuronium. Patients were observed four-hourly for pain using an 11-point verbal rating scale (VRS). Nausea and vomiting, and sedation were assessed using four-point scales post-operatively. Vital signs, request for rescue anti-emetic and analgesic, and overall satisfaction were recorded. Results: The mean nausea scores were lower in Group 2 (1.00 +/- 1.33 vs 0.06 +/- 0.25 at 0-8 hr, 1.22 +/- 1.93 vs 0.06 +/- 0.25 at 8-16 hr; P < 0.01; 0.81 +/- 1.68 vs 0 at 32-40 hr, P < 0.05: Group 1 vs Group 2). The vomiting scores were also lower (0.50 +/- 1.04 vs 0 at 0-8 hr, 0.67 +/- 1.50 vs 0 at 8-16 hr: P < 0.05; Group 1 vs Group 2). Seven (39%) patients in Group 1, but none in Group 2 requested rescue anti-emetic (P < 0.01), There were no differences in VRS, sedation score, overall satisfaction or vital signs. Conclusion: Tramadol and droperidol combination is superior to tramadol alone for post-operative PCA. It provides a similar quality of analgesia with less nausea and vomiting and without an increase In sedation.