This multicentric randomized trial compared two strategies in the prevention of acute and delayed nausea and vomiting induced by moderately emetogenic chemotherapy in patients with breast cancer. The antiemetic efficacy and side effects of oral granisetron, followed by metoclopramide, were compared to those of intravenous (IV) ondansetron followed by oral ondansetron. 198 chemonaive patients with breast cancer, treated with a moderately emetogenic chemotherapy, were randomly assigned to receive either oral granisetron 1 mg twice a day on day 1, followed by metoclopramide, 60 mg on day 2 and 3, or ondansetron, 8 mg IV on day 1, followed by ondansetron 8 mg tablet twice a day on day 2 and 3. Both treatments have shown similar control of acute emesis: complete response was achieved in 71% of granisetron group and 66% of ondansetron, and total response in respectively 49% and 53%. However, granisetron plus metoclopramide showed a trend towards better efficacy than oral ondansetron in the prevention of delayed emesis. Furthermore, during the overall study period (day 1 to 5), the percentage of complete responses in the group receiving oral granisetron followed by oral metoclopramide was significantly higher than in the group receiving ondansetron (53% versus 37%; p = 0.022). In conclusion, oral granisetron has shown similar efficacy as IV ondansetron in the prevention of acute emesis induced by moderately emetogenic chemotherapy. Oral granisetron followed by metoclopramide seems more efficient than IV plus oral ondansetron in the prevention of delayed emesis.