Epidurally administered dexamethasone might reduce postoperative pain. However, the effect of epidural administration of dexamethasone on postoperative epidural analgesia in major abdominal surgery has been doubtful. To investigate the effects and optimal dose of epidural dexamethasone on pain after major abdominal surgery. A prospective randomized, double-blind study. University hospital. One hundred twenty ASA physical status I and II men, scheduled for gastrectomy, were enrolled. Patients were randomly assigned to receive one of 3 treatment regimens (n = 40 in each group): dexamethasone 5 mg (1 mL) with normal saline (1 mL) (group D) or dexamethasone 10 mg (2 mL) (group E) or 2 mL of normal saline (group C) mixed with 8 mL of 0.375% ropivacaine as a loading dose. After the surgery, 0.2% ropivacaine - fentanyl 4 ?g/mL was epidurally administered for analgesia. The infusion was set to deliver 4 mL/hr of the PCEA solution, with a bolus of 2 mL per demand and 15 minutes lockout time. The infused volume of PCEA, intensity of postoperative pain using visual analogue scale (VAS) during rest and coughing, incidence of postoperative nausea and vomiting (PONV), usage of rescue analgesia and rescue antiemetic, and side effects such as respiratory depression, urinary retention, and pruritus were recorded at 2, 6, 12, 24, and 48 hours after the end of surgery. The resting and effort VAS was significantly lower in group E compared to group C at every time point through the study period. On the contrary, only the resting VAS in group D was lower at 2 hours and 6 hours after surgery. Total fentanyl consumption of group E was significantly lower compared to other groups. There was no difference in adverse effect such as hypotension, bradycardia, PONV, pruritis, and urinary retention among groups. Use of epidural PCA with basal rate might interrupt an accurate comparison of dexamethasone effect. Hyperglycemia and adrenal suppression were not evaluated. Epidural dexamethasone was effective for reducing postoperative pain. Especially, an epidural dexamethasone dose of 10 mg was more effective than a lower dose in patients undergoing gastrectomy which was associated with moderate to severe postoperative pain.