Objective: The objective was to separately compare effectiveness of 1.25 mg of intravenous (IV) droperidol and 8 mg of IV ondansetron with 0.9% saline placebo for adult emergency department (ED) patients with nausea. A novel primary outcome measure, expected to aid clinical interpretation of reported results, was employed. Methods: A randomized controlled trial was conducted at the three EDs of Monash Health, Melbourne, Australia. The design was to demonstrate superiority of the active drugs over placebo. The primary outcome measure of symptom improvement was defined as a visual analog scale (VAS) rating change of –8 mm or more from baseline at 30 minutes posttreatment. Mean VAS changes per group and percentages experiencing the desired treatment effect were also compared. The study was concluded after recruitment of 215 of the planned 378 patients, as interim analysis confirmed that continuation could not result in a finding of superiority. Results: Of 215 patients, 73 (34%), 71 (33%), and 71 (33%) received droperidol, ondansetron, and placebo. Symptom improvement occurred in 75% (95% confidence interval [CI] = 64% to 85%), 80% (95% CI = 69% to 89%), and 76% (95% CI = 64% to 85%), respectively. Mean VAS changes were –29 mm (95% CI = –36 to –23 mm), –34 mm (95% CI = –41 to –28 mm), and –24 mm (95% CI = –29 to –19 mm), respectively. Desired treatment effects were experienced by 77% (95% CI = 65% to 86%), 73% (95% CI = 61% to 83%), and 59% (95% CI = 47% to 71%), respectively. Conclusion: For adult ED patients with nausea, superiority was not demonstrated for droperidol or ondansetron over placebo.