Chemotherapy-induced nausea and vomiting(CINV)is one of the side effects causing significant psychological and physical suffering in patients receiving chemotherapy. First-generation 5-HT3 receptor antagonists(ondansetron, granisetron and ramosetron)are available, but some patients are still not treated adequately. Palonosetron is a second-generation 5-HT3 receptor antagonist with a prolonged duration of action and a higher receptor binding affinity than first-generation agents. In the present study, we aimed to compare the antiemetic efficacy of palonosetron vs. ramosetron in preventing acute and delayed CINV. Patients received palonosetron followed by ramosetron, and the antiemetic effects were evaluated by the Multinational Association of Supportive Care in Cancer Antiemesis Tool(MAT). A total of 22 patients with colon cancer receiving chemotherapy were included in the efficacy analyses. Nine patients were observed with acute nausea, and 11 patients with delayed nausea. Relief of symptoms was observed in 3 patients with acute nausea and 4 patients with delayed nausea by switching from ramosetron to palonosetron. There was no significant difference of improvement in the acute phase, there was significantly suppressed in the delayed phase.