PURPOSE: A retrospective study was intended to assess the incidence, severity, and risk factors of abdominal radiotherapy induced nausea and vomiting and to evaluate the effect of antiemetic drugs like metoclopramide and ondansetron. MATERIALS AND METHODS: From October 1997 to October 1999, we enrolled 48 patients who received conventional fractionated radiotherapy on abdomen. Patients under 18 years old and who received concomittant chemotherapy were excluded. Evaluation was carried out on the basis of daily check of the intensity of nausea and any episode of vomiting and retching. RESULTS: Nausea and vomiting occurred in 65% and 25% of patients, respectively. On multivariate analysis, previous experience with chemotherapy was the only significant patients-related risk factor. The irradiated site and field size were also significant in terms of radiotherapy-related risk factors. Nausea and vomiting were markedly diminished in the group given ondansetron. CONCLUSION: Our study offered useful data on general picture of radiation induced nausea and vomiting in patients given conventional fractionated radiotherapy on abdomen. For the patients with risk factors, prophylactic antiemetic drug prescription may be mandatory to enhance compliance with radiotherapy and ondansetron is more effective than metoclopramide for controlling nausea and vomiting.