The physicians and nurses managing the patient during surgery and in the recovery room, the personnel involved with postoperative pain assessment and management of the intrathecal infusion, and the study patients will be blinded to group assignments. Treatment assignment codes will not be available to the investigators until all patients completed the study. A global pain score using the visual analogue scale (VAS) with 0 corresponding to "no pain" and 10 to "the worst imaginable pain" for the patient will be obtained before surgery. In the operating room, patients will be sedated with midazolam (0.05 mg/kg titrated to effect) and an intrathecal catheter placed in the sitting position, at the L3-4 or L4-5 vertebral level to deliver spinal anesthesia with bupivacaine 0.5%, (7.5 mg) and fentanyl 25mcg. Subjects will be maintained at normothermia in the operating room. A sensory analgesic level of T10 will be obtained prior to commencement of surgery. At completion of surgery an intrathecal infusion of fentanyl 0.5 mcg/ml and bupivacaine 0.1 mg/ml will be initiated using a continuous basal infusion with superimposed patient controlled intrathecal analgesia (PCIA) bolus doses. Initial infusion rates will be 4 ml/h basal intrathecal infusion plus PCIA of 1 ml q 12 min with a 4-hour lockout of 40 ml. The patients will be instructed prior to surgery to use PCIA mode at their discretion to maintain the VAS pain score <4, following a previously applied protocol (6). A standardized surgical technique will be used in all subjects.