OBJECTIVE To assess the efficacy of postoperative continuous lumbar plexus blocks for postoperative pain control in patients undergoing open reduction and internal fixation of an acetabular fracture. METHODS Twenty-six patients who underwent open reduction and internal fixation of an acetabular fracture. DESIGN/PERSPECTIVE: According to a case-control study design, patients were divided into 2 groups: Group 1 (n = 13) received postoperatively a continuous lumbar plexus block with 0.2% ropivacaine (10 mL/hr for 48 hours), and group 2 (n = 13) received postoperatively patient-controlled analgesia with morphine (1 mg; lock-out time, 10 minutes; total 6 mg/hr). METHODS Postoperative morphine consumption, time to unassisted ambulation, and clinical and radiographic outcomes. RESULTS No significant differences in demographics, surgical procedure, or duration of surgery were reported between the two groups. The lumbar plexus catheter group showed a lower requirement for morphine in the postanesthesia care unit (6 mg [0-14 mg]) and during the first 2 days (20 mg [6-55 mg] on day 1 and 29 mg [4-56 mg] on day 2) than the control group (51 mg [20-100 mg] on day 1 and 50 mg [10-93 mg] on day 2) (P = 0.001 and P = 0.021). Effective unassisted ambulation was recovered earlier in patients with the lumbar plexus catheter (3 days; range 2-4 days) than in the control group (4 days; range 3-7 days) (P = 0.015). CONCLUSIONS Continuous lumbar plexus block represents an interesting alternative for postoperative pain control in patients undergoing open reduction and internal fixation of an acetabular fracture.