Background: Epidural steroid injection(ESI) is often adminstered to treat lower back pain, but its effect iveness on postepidural backache have not yet been determined. Methods: Sixty patients scheduled for cesarean section under epidural anesthesia were randomly assigned to receive, 1 ml of normal saline(Group 1), or 5 mg of dexamethasone (Group 2), epidurally via indwelling catheter after delivery. Results: The incidences of postepidural backache occured significantly more often in Group 1(56.7%) than in Group 2(26.7%)(P<0.05). There was a significant association between postepidural backache and multiple attempts at epidural needle placement. Conclusion: Epidural dexamethasone has a preventive effect on postepidural backache.