Postoperative nausea and vomiting is a troublesome problem in pediatric patients undergo- ing strabismus surgery. We compared the effects of ondansetron with those of droperidol and placebo within the 24hrs postoperative period. 54 children, who admitted to Presbyteri- an Medical Center to receive strabismus operations, with ASA physical status 1, were as- signed to one of three groups according to uncontrolled parallel comparative study design. A standard anesthetic technique consisting of thiopental-vecuronium for induction and N2O-O2-enflurane for maintenance of anesthesia was used. The data showed that ondansetron 0. 067mg/kg i.v. before induction was significantly more effective in preventing emesis (n=19, 100%) than placebo(n=17, 58.8%). But, there was no significant difference between droperidol group and placebo group. In conclusion, ondansetron(0.067mg/kg) given intravenously before induction to prevent postoperative nausea and vomiting in patients undergoing elective strabismus surgery in children was effective.