Objective:To evaluate the effect of single-dose ondansetron in prevention of chemotherapy-induced nausea and vomitus in lung cancer patients.Methods:35 lung cancer patients receiving chemotherapy were observed with self-comparisonal design.A single dose of 8mg ondansetron and of 20mg metoclopramide were administered by intravenous injection and intramuscular in jection to the patients at different time and the outcome was observed.Results:The control rates of nausea and vomitus by ondansetron were 91.4% and 94.3%,and 65.7% and 74.3% by metoclopramide respectively(P＜0.05).Conclusion:A single-dose of ondansetron can effectively prevent nausea and vomitus in lung cancer patients caused by chemotherapy.