Recently, the availability of 5-hydroxytryptamine-3 antagonists has provided better protection from chemotherapy-induced emesis. These drugs, in combination with dexamethasone, are more expensive but more cost-effective than the alternative antiemetic regimens in the prevention of acute emesis induced by high single dose and low and repeated doses of cisplatin and, probably, of acute emesis induced by moderately emetogenic chemotherapy. In the prevention of emesis induced by oral cyclophosphamide-methotrexate-fluorouracil and in the prevention of delayed emesis induced by cisplatin and moderately emetogenic chemotherapy, the most cost-effective choices are represented, respectively, by a combination of intravenous dexamethasone on day 1 and 8 plus 14-day oral metoclopramide (a combination of oral dexamethasone plus metoclopramide and oral dexamethasone alone). In all cases, the 5-hydroxytryptamine-3 antagonists should be used only in patients in whom the most cost-effective antiemetic regimens either fail or are not tolerated.