BACKGROUND: This prospective randomized double-blinded study was designed to compare the efficacy of a combination of high dose metoclopramide and dexamethasone with that of haloperidol, midazolam and dexamethasone, for the prevention of postoperative nausea and vomiting (PONV) in patients scheduled for laparoscopic gynecologic surgery who are receiving fentanyl intravenous-patient controlled analgesia. METHODS: The subjects were randomly allocated to either group M (20 mg metoclopramide and 10 mg dexamethasone was administered at induction, n = 35) or group H (1 mg haloperidol, 3 mg midazolam and 10 mg dexamethasone were administered at induction, n = 35). The incidence of PONV and the severity (measured by numeric rating scale) of the patients' nausea and pain were evaluated at 6 hours, 24 hours, and 48 hours, postoperatively. RESULTS: The overall incidence of the PONV was not significantly different between the two groups during the 48 hours period (group M: 21% vs. group H: 12%). The severity of the nausea and pain were similar between the two groups. CONCLUSIONS: The prophylactic use of a combination of 1 mg haloperidol, 3 mg midazolam and 10 mg dexamethasone is as effective and inexpensive as 20 mg metoclopramide and 10 mg dexamethasone to prevent PONV.