Chemotherapy-induced nausea and vomiting (CINV) is still one of the most disturbing side-effects of cancer treatment. CINV often causes non-compliance with treatment, unwillingness, nutritional deficits and impairment of QOL, leading to poor outcomes of treatment. Therefore, we need to conduct adequately optimized antiemetic therapy based on the antiemetic guidelines. CINV is classified into categories; acute onset, delayed onset, and anticipatory CINV. Although the precise mechanism of CINV is not fully understood, it is generally accepted that CINV is mediated through the chemoreceptor trigger zone (CTZ). 5-Hydroxytryptamine (5-HT3) and serotonin receptors are especially important in acute CINV. 5-HT3 receptors are localized to CTZ of brain and peripheral vagal nerve terminus. Activation of the vomiting center is caused by direct stimulation of 5-HT3 receptors by anticancer drugs. The substance P is localized in central and peripheral nervous systems and induces CINV by binding to neurokinin-1 (NK-1) receptor. Substance P plays a predominant role in delayed CINV. Anticipatory CINV is associated with psychological conditioning. Therefore, it is important to prevent anticipatory CINV in the first cycle of chemotherapy. Chemotherapeutic agents are classified into four emetic risk groups; highly (90%), moderately (30–90%), low (10–30%) and minimally (<10%) emetogenic. The antiemetic guideline published by Japanese Society of Clinical Oncology recommends the selection of specific antiemetic regimen based on risk of CINV. There are three major antiemetic agents; 5-HT3 receptor antagonist, dexamethane and NK-1 receptor antagonist. A combination of all the three antiemetic agents is recommended for the highly emetic agents. A combination of 5-HT3 receptor antagonist and dexamethane is recommended for the moderately emetogenic agents. On the other hand, premedication of only dexamethasone is recommended for low emetogenic agents. Antiemetic is not recommended for minimally emetogenic agents.