BACKGROUND: Epidural analgesia, via either a thoracic or lumbar route, is commonly used to provide postoperative analgesia following thoracotomy for pulmonary resection, but little data indicate which location is better in terms of postoperative analgesia, side effects, or associated complications. METHODS: 54 patients, who undergo a lateral thoracotomy, were randomized to receive a mixture of fentanyl and 0.15% bupivacaine at 0.5microgram/kg/hr of fentanyl via either a thoracic (Group T) or a lumbar (Group L) catheter. Postoperative pain was assessed 6hrs after the operation and everyday for 5 days on a visual analog scale (VAS). Postoperative side effects and patients satisfaction of epidural analgesia were assessed by 4 grades system. RESULTS: The VAS scores during coughing were higher than those of resting state without intergroup differences. The incidences and severity of side effects (nausea, vomiting, pruritus, sedation) were not different between group T and group L, but the incidence of urinary retention attributable to use of the lumbar epidural route was significantly higher than with the thoracic route (p<0.05). CONCLUSIONS: The authors conclude that there is no clinical advantage of thoracic over lumbar epidural fentanyl in the thoracotomy patients with respect to analgesia and incidences of most side effects except urinary retention.