The effect of three solutions on postoperative pain relief by continuous epidural infusion was studied. Seventy-five patients after upper or lower abdominal surgeries were assigned to one of three groups and the postoperative pain relief was evaluated for 48 hours. Group I: bolus injection of buprenorphine (Bn) 0.1 mg + saline (S) 8 ml and continuous infusion (2 ml.h-1) of Bn 0.8 mg + S 92 ml; Group II: bolus injection of Bn 0.1 mg + 0.5% bupivacaine (Bc) 4 ml + S 4 ml and continuous infusion of Bn 0.8 mg + S 92 ml; Group III: bolus injection of Bn 0.1 mg + 0.5% Bc 4 ml + S 4 ml and continuous infusion of Bn 0.8 mg + 0.5% Bc 40 ml + S 60 ml. The combination of buprenorphine with low-dose bupivacaine (Group III) offered the most effective postoperative analgesia in three groups without increasing the frequency of adverse effects induced by epidural administration of local anesthetics. However, even in Group III, the percentage of patients complaining of pain at bed rest was still high during early postoperative period (56% at 6 hours postoperatively). The results suggest that further consideration is necessary on agents selection and dosage adjustment for the postoperative epidural analgesia.