Intravenous 5-hydroxytryptamine3 (5-HT3) receptor antagonists are now established antiemetics in the treatment of chemotherapy-induced emesis. For optimal convenience and acceptability, oral therapy is desirable. Retrospective comparisons indicate that oral granisetron may have an efficacy comparable with that of intravenous granisetron. Recent new data are available on the use of granisetron in the prophylaxis of acute emesis in randomized, double-masked trials. After moderately emetogenic chemotherapy, the optimal regimen appears to be 1 mg twice daily, although 2 mg once daily is equally effective. Oral granisetron is significantly superior to oral prochlorperazine. After high-dose cisplatin chemotherapy, oral granisetron is as effective as metoclopramide plus dexamethasone; the addition of dexamethasone further enhances its efficacy. Oral granisetron was well tolerated in all these trials. Headache and constipation were the most common adverse events, as has been reported for other 5-HT3 receptor antagonists. No randomized trials of oral-only tropisetron or dolasetron have yet been published.