The objective of the present study was to examine the problem of the control of nausea and vomiting induced by non-cisplatin containing cyclophosphamide-based chemotherapy regimens in breast cancer patients. This was randomized, double-blind, parallel-group and placebo-controlled study comparing the efficacy of three antiemetic therapeutic regimens (ondansetron for 3 days, ondasetron plus metoclopramide, and ondansetron given in a single dose) in breast cancer patients receiving cyclophosphamide-based chemotherapy regimens on an outpatient basis. Both the primary and the secondary efficacy were measured. The primary efficacy variable was the number of emetic episodies (considering early and delayed emesis). The secondary efficacy variable measured was the quality of life. Two-by-two tables using the chi-square test and relative-risk concept were elaborated for statistical analysis. There was no difference between high-dose ondansetron and ondansetron plus metoclopramide among patients given CMF (cyclophosphamide, methotrexate, 5-fluorouracil). The single-dose ondansetron regimen showed the worst results. In patients given an FEC regimen (cyclophosphamide, epirubicin, 5-fluorouracil) the antiemetic efficacy was best for the high-dose ondansetron regimen, followed by the ondansetron plus metoclopramide regimen, and was worst for single-dose ondansetron administration. Despite the use of different antiemetic schedules, nausea and emesis are significant problems in patients receiving cyclophosphamide-based chemotherapy. Their adequate control should be the aim of any antiemetic approach.