Background: The aim of our study was to evaluate the antiemetic effects of intravenous dexamethasone in preventing continuously infused epidural morphine-related nausea and vomiting. Methods: Twenty-seven patients requiring general anesthesia for gastrectomy were enrolled in a randomized, double-blinded, and placebo-controlled study. At the end of surgery, all patients received epidural morphine 3 mg and were connected to an epidural morphine infusion pump for 2 days in order to relieve postoperative pain. Before the morphine injection, the dexamethasone group (n = 12) received IV dexamethasone 10 mg, whereas the saline group (n = 15) received IV saline. The incidence of nausea & vomiting, pruritus, back pain and VAS scores were assessed in the recovery room, and at 24 h and 48 h postoperatively. Results: There was no significant difference in the total incidence of nausea and vomiting, pruritus, back pain or in the VAS scores. However, there was no vomiting and no back pain in the dexamethasone group. Conclusions: Intravenous dexamethasone did not significantly decrease the total incidence of nausea or vomiting in patients receiving continuous epidural morphine for postoperative pain control. However, IV dexamethasone appears to decrease the severity of nausea, vomiting and back pain.