This prospective randomized single-blinded study was conducted to determine whether there were differences in consumption, demand dosing and postoperative analgesia quality between PCEA using ropivacaine and levobupivacaine. Seventy patients with ASA classification I and II aged 18 to 80 years old scheduled for elective total knee replacement or total hip replacement were studied. All patients received CSE and then were randomly allocated to receive either ropivacaine 0.165% (Group A) or levobupivacaine 0.125% (Group B) both added with fentanyl 2.0 mcro g/ml via epidural route. PCEA regime was offered for 48 hours with additional standard orthopaedic practice of oral analgesia (etoricoxib 120 mg OD and paracetamol 1.0 gm QID) on the second postoperative day. Basal infusion of PCEA was at 3.0 ml/hour and discontinued after 24 hours following started of PCEA. The consumption of local anaesthetics used within the first 24 hours (basal + demand) and 48 hours (total basal + total demand) were recorded. The VAS pain score, sedation score, side effects and vital signs (blood pressure, heart rate and respiratory rate) were also recorded every four hours for 48 hours. This study showed that the total volume of drug used was significantly higher in Group A (163.31+/- 29.01 ml) than Group B (142.69 +/- 30.93ml) (p<0. 01). The mean dose of Group A for the first 48 hours after surgery was 251.43 +/- 70.02mg and was significantly greater than the mean dose of Group B (178.91 +/-42.33 mg) (p<0.01). The numbers of PCEA boluses delivered (D) and PCEA attempts (A) were higher in the Group A (22.37 +/-7.32 and 27.66 +/- 9.12) in contrast to Group B (17.63 +/- 7.71 and 24.40 +/- 11.51) but the differences were not statistically significant. The ratio D/A showed significantly higher in Group A (0.83 +/- 0.13) than Group B (0.74 +/- 0.15) (p<0. 02). The VAS pain score was similar for both groups. One patient in Group B had vomiting and there was no sedation, hypotension, pruritus or motor block recorded in both groups. In conclusion this study showed that both PCEA using ropivacaine 0.165% with fentanyl 2.0 micro g/ml and levobupivacaine 0.125% with fentanyl 2.0 micro g/ml provided effective postoperative analgesia within the first 48 hours of major lower limb orthopaedic surgery despite clinically significant dose difference. There was no hypotension, pruritus, sedation or motor block recorded in both groups.