Abstract: In this research we evaluated the antiemetic efficacy of ondansetron and metoclopramide. 30 patients received ondansetron and 12 of these had been used metoclopramide before they were giv-en ondansetron. Patients receiving ondansetron had a higher rate of complete control of emesis than these used metoclopramide (63.30ovs. 16.7%，P<0.001). The response rate is higher as well (96" 7%vs. 58.3%，P<0. 001).Side effects of ondansetron were mild We conclude that on-dansetron has a highly antiemetic efficacy and is significantly superior to meto.l opramide for cotrolling emesis associated with tumor chemotherapy.