Management of acute postoperative pain should be of great interest for all hospital institutions. This study compared the efficacy of epidural morphine sulphate with a combination of epidural morphine sulphate and magnesium sulphate administered to control postoperative pain in the first 24 hrs in patients of lower extremity vascular surgery , with respect to pain scores at rest and at movement , duration of analgesia, total morphine requirements , hemodynamic stability and side effects if any.Methods: 120 patients, ASA I/II were enrolled into the study . All patients had a combined spinal- epidural anaesthesia and after surgery completed , as the sensory blockade regressed to L1, patients were randomized by closed envelop technique into one of three groups , Group C : (n=40) patients received an initial bolus of epidural 4 mg morphine sulphate in 6 ml 0.9 normal saline , Group M50 : (n=40) patients received an initial bolus of epidural 4 mg morphine sulphate plus 50 mg of magnesium sulphate in 6 ml 0.9 normal saline , Group M100 : (n=40) patients received an initial bolus of epidural 4 mg morphine sulphate plus 100 mg of magnesium sulphate in 6 ml 0.9 normal saline.Results: The results of this study demonstrated that there were significant lowering of pain scores both at rest and at movement with significant prolongation of duration of analgesia and significant lowering of total morphine requirements in first 24 hrs in patients with epidural morphine sulphate plus epidural magnesium sulphate compared to patients with epidural morphine sulphate . Hemodynamic variables were stable and side effects were also comparable and there were no significant differences beween groups. Conclusion: In the present clinical study , epidurally administered magnesium sulphate is shown to prolong the duration of morphine sulphate analgesia without significant side effects.