This paper described an outline of clinically applications of 5-HT3 receptor antagonists, mainly on ondansetron, which control nausea and vomiting associated with cancer chemotherapy. Clinically, 5-HT3 receptor antagonists demonstrated significantly superior antiemetic effects to metoclopramide which has been prescribed for relatively long time. The response rates for granisetron and those for ondansetron were different due to the different categorical scales. However, when the same scale was applied, similar efficacies have been observed. Introduction of the tablet form may well broaden the clinical applications. Considering the highly evaluated safety, 5-HT3 receptor antagonists, from the viewpoints of clinical usefulness and safety, seems to be useful drugs for controlling nausea and vomiting associated with cancer chemotherapy.