BACKGROUND: Intravenous lidocaine has been reported previously to inhibit neuropathic pain. But it`s analgesic effect in postoperative pain has provided controversial results. The object of this study was to define the analgesic effect of intravenous lidocaine in addition to morphine on postoperative pain control. METHOD: Female patients scheduled for total abdominal hysterectomy were randomly assigned to one of two groups to be studied in a double-blind manner. Group M (n=20) and Group M+L (n=18) received intravenous morphine (0.1 mg/kg) or intravenous morphine (0.1 mg/kg) + lidocaine (30 mg), respectively, after closure of the peritoneum. Continuous infusion of morphine (1.5 mg/hr) or morphine (1.5 mg/hr) + lidocaine (60 mg/hr) was started immediately after i.v. bolus injection, respectively, until the end of the operation. Postoperative pain was managed with a PCA pump (Walkmed, Medex, USA), setting the basal rate of morphine (0.5 mg/hr) + bolus dose (1.5 mg) and lock out time of 10 min in group M, adding the lidocaine (basal rate: 20 mg/hr and bolus dose: 60 mg) to the same dose of morphine as group M in group M+L. Postoperative visual analogue pain scores (VAS), analgesic requirements and side effects were examined for 2 days postoperatively and compared between groups. RESULTS: VAS at movement were significantly less (p< 0.05) in group M+L than in group M of 2, 12, 24, 36 and 48 hrs after surgery. Patient-controlled morphine cumulative consumption in group M+L was significantly less (p< 0.05) than in group M for 24 hours (26.3 mg vs 35.3 mg) after the operation (p<0.01). CONCLUSIONS: Intravenous lidocaine reduces postoperative pain at movement and analgesic requirements. These results suggest that low-dose adminstration of i.v. lidocaine attenuates the postoperative hyperalgesic state.