Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life. The emetogenicity of the chemotherapeutic agents, repeated chemotherapy cycles, and patient risk factors (female gender, younger age, alcohol consumption, history of motion sickness) are the major risk factors for CINV. The use of 5-hydroxytryptamine3 (5-HT3) receptor antagonists plus dexamethasone has significantly improved the control of acute CINV, but delayed nausea and vomiting remains a significant clinical problem. Although the 5-HT3 receptor antagonists, dexamethasone, and metoclopramide have been used to prevent delayed CINV, only dexamethasone appears to have much efficacy with acceptable toxicity. Recent studies have introduced two new agents, palonosetron and aprepitant, for the prevention of both acute and delayed CINV. Palonosetron is a new 5-HT3 receptor antagonist with a longer half life and a higher binding affinity than older 5-HT3 receptor antagonists. It improves the complete response rate (no emesis, no need for rescue) of acute and delayed CINV in patients receiving moderately emetogenic chemotherapy compared to the older 5-HT3 receptor antagonists.The other agent, aprepitant, is the first agent available in the new drug class of neurokinin-1 receptor antagonists. When added to a standard regimen of a 5-HT3 receptor antagonist and dexamethasone in patients receiving highly emetogenic chemotherapy, it improves the complete response rate of acute CINV. Aprepitant also improves the complete response of delayed CINV when compared to placebo and when used in combination with dexamethasone compared to dexamethasone alone. Acute and delayed nausea may also be improved by aprepitant when used in combination with a 5-HT3 and dexamethasone prechemotherapy or with daily dosing for 3-5 days following chemotherapy. Based on these studies, new guidelines for the prevention of CINV are proposed. Future studies may consider the use of palonosetron and aprepitant with current and other new agents (olanzapine, gabapentin) in moderately and highly emetogenic chemotherapy, as well in the clinical settings of multiple-day chemotherapy and bone marrow transplantation.