Post-thoracotomy pain is so severe that may lead to postoperative complications, such as sputum retention, atelectasis, pneumonia and respiratory failure. These complications are associated with shallow breathing and inability to cough due to pain. To reduce postoperative pulmonary complications and improve respiratory mechanics, effective pain relief is essential. Among the many methods, epidural administrations of narcotics or local anesthetics have been shown to provide profound relief of postoperative pain. Forty-five patients undergoing thoracotomy were randomized into three groups based on a postoperative pain regimen as indi-cated: Group I; intermittent intramusculal injections of nalbuphine 0.2mg/kg for pain control(n= 15) Group II; intermittent epidural injections of mixtures of 0.2% bupivacaine and fentanyl 3 ug/ ml (n=15) Group III: continuous epidural infusion of mixtures of 0.2% bupivacaine and fentanyl 3 ug/ml at a rate of 4-5 ml/hr with supplementation on pain complaint. We evaluated postoperative pain score at 30 minutes, 8 hours, 16 hours, 24 hours, 32 hours, 40 hours, and 48 hours after thoracotomy. And we observed the duration of analgesia and the incidence of systemic side effects of three methods. The results were as follows; 1) The pain score was significantly decreased in group III compared to group I and II<0. 05). 2) The mean duration of analgesia was significantly longer in group III compared to group I and II(p<0.05). 3) the number of case of systemie side effects in group I was one case of nausea and vomiting, in group II, two cases of mild hypotension, and one case of nausea and vomiting, pruritus, headache, and urinary retention each respectively and in group III, one case of ruinary retention.