BACKGROUND: Nausea and vomiting are among the most common postoperative complaints. There is high incidence of emesis after middle ear surgery and opioids increase the prevalence of postoperative nausea and vomiting. METHODS: Sixty six adult patients undergoing routine tympanomastoidectomy under general anesthesia were divided into two groups to study the incidence and effect of intraoperative fentanyl as supplements on postoperative nausea and vomiting. Patients in group 1 received medical air instead of N2O about 15 minutes before grafting, while patients in group 2 received not only medical air instead of N2O, but also intravenous fentanyl (1~1.5 microgram/kg). RESULTS: The incidences of nausea and vomiting in the group 1 and 2 were 19.4% and 22.9%, respectively. There was no significant difference of postoperative nausea and vomiting between the group 1 and group 2 (P=0.73). CONCLUSION: The incidence of nausea and vomiting after tympanomastoidectomy in adult was not higher than comprehensive that of recent other reports and a small dose of fentanyl, given intraoperatively for supplementation, did not increase the prevalence of nausea and vomiting.