BACKGROUND: Continuous epidural morphine administration (CEM) is a common method to treat the pain of terminal cancer patients, but this could produce many side effects/ such as pruritus, nausea, vomiting, constipation and urinary retention. The purpose of this study was to determine the optimal epidural butorphanol dosage to prevent side effects of CEM in terminal cancer patients. METHODS: Thirty terminal cancer patients were randomly assigned to one of three groups. After insertion of epidural catheter, morphine 2 mg and butorphanol 1 mg were injected epidurally for a loading dose and a 2 Day Infusor (2 ml/hr)(Home Pump(R) , I-Flow, Lake Forest, USA) containing morphine 8 mg with butorphanol 2 mg (B2 group, n = 10), 4 mg (B4 group, n = 10) or 6 mg (B6 group, n = 10) mixed with 5% D/W (total 100 ml) was connected. Severity of pain, nausea and vomiting, and pruritus were evaluated using VAS score at 1, 6, 12, 24, 36 and 48 hr after epidural infusion. RESULTS: Severity of pain, nausea and vomiting, and pruritus were significantly decreased in the B6 group as comparable to the other two groups (p < 0.05). CONCLUSIONS: The addition of butorphanol 3 mg to morphine 4 mg in CEM in terminal cancer patients reduced nausea, vomiting and pruritus and improved the pain control effect.