BACKGROUND: The purpose of this study was to evaluate the efficacy of intravenous clonidine-fentanyl to prevent postepidural shivering in patients undergoing an elective orthopedic surgery. METHODS: Forty ASA class 1 or 2 patients who received epidural anesthesia for an orthopedic surgery were allocated randomly to two groups. 10 min before epidural anesthesia group 1 received intravenous clonidine 2.0ng/kg and group 2 received clonidine 1.0ng/kg and fentanyl 1.0ng/kg shivering was determined objectively by observing involuntary muscle activity. Mean arterial pressure, heart rate and sedation score were measured at 5 minute intervals during the first 30 minutes following epidural anesthesia. RESULTS: There were no significant differences between the two groups in the occurrence of shivering, hemodynamic changes and sedation score. CONCLUSIONS: Intravenous clonidine 2.0ng/kg and the combination of clonidine 1.0ng/kg and fentanyl 1.0ng/kg were not significantly different in occurrence of postepidural shivering. Therefore, a combination of small doses of intravenous clonidine and fentanyl may be safe and useful to reduce postepidural shivering.