A large number of different 5-hydroxytryptamine (HT)(3) receptor antagonists have been marketed with the indication of preventing nausea and vomiting induced by chemotherapy--palonosetron is the most recently developed of these. Pharmacologic studies have revealed that palonosetron has a long half-life, a high affinity for 5-HT(3) receptors, exhibits allosteric binding to 5-HT(3) receptors and possess positive cooperativity. Although interesting, pharmacologic differences are only useful if they result in clinical advantages, such as an increase in efficacy and/or an improvement in tolerability. We summarize preclinical and clinical studies of palonosetron and compare the efficacy and tolerability with the other 5-HT(3) receptor antagonists, ondansetron, granisetron and dolasetron.