BACKGROUND: The purpose of this study was to evaluate the analgesic effect and side effects including respiratory depression and cardiovascular changes after continuous high thoracic epidural infusion of morphine when given with bupivacaine for postthoracotomy pain. METHODS: In a prospective study, 25 patients who received continuous thoracic epidural administration of morphine with bupivacaine after thoracotomy were studied. The analgesia was provided by a continuous epidural infusion for 2 days. Initially, 0.25% bupivacaine 5~7 ml with morphine 1 mg was injected epidurally. Then, continuous epidural infusion of 0.25% bupivacaine 2 ml/hr with morphine 0.125 mg/hr was followed. RESULTS: The pain score (visual analogue pain scale) was below 3 at all postoperative periods except postoperative 1 hour with cough. The significant PaCO2 and cardiovascular changes for 2 days after epidural injection were not occured. There were no significant side effects requiring treatment. CONCLUSION: Continuous high thoracic epidural administration of 0.125 mg/hr of morphine with 0.25% bupivacaine is safe and effective analgesic method for thoracotomy.