BACKGROUND: Better effect of antiemetic drugs can be obtained by combination of multiple antiemetic drugs that have different mechanisms of action. However, if the combined drugs have similar mechanisms of action, the incidence of side effects may be increase. This study was conducted to evaluate the ability of using combination therapy consisting of metoclopramide and dexamethasone in control of postoperative nausea and vomiting. METHODS: Sixty adult female patients undergoing major gynecological operation under the general anesthesia were randomly divided into two groups according to administered drugs. The patients received a single IV dose of metoclopramide (10 mg, Group I) or metoclopramide plus dexamethasone (10 mg 8 mg, Group II) when as operator sutured the skin wound. The incidences of nausea and vomiting were assessed during the first 12, 24, and 48 hours after recovery from anesthesia. RESULTS: There were no prominent incidences of postoperative nausea and vomiting between two groups within postoperative 12 hours. But there were significantly increased incidences of nausea and vomiting in Group I (26.7%, 13.3%) compared to Group II ( 8.0%, 3.2%) during postoperative 24 hours and 48 hours. CONCLUSIONS: Combination therapy of metoclopramide with dexamethasone seemes to have no synergic effect in control of postoperative nausea and vomiting.