The approach to the treatment of nausea and vomiting in a cancer patient should begin with a complete assessment, including the frequency, duration, and intensity of the nausea/vomiting; associated activities; and whether anorexia or cachexia is present. It is important to determine whether the nausea and vomiting is related to treatment (chemotherapy, radiation) or is independent of cancer treatment. Nausea/vomiting unrelated to chemotherapy and/or radiation may have an etiology for which there is a specific and potentially successful intervention. Various national and international antiemetic guidelines have been developed for the prevention of chemotherapy- and radiotherapy-induced nausea and emesis. The antiemetics recommended in these guidelines (5-hydroxytryptamine type 3 receptor antagonists, neurokinin-1 receptor antagonists, dexamethasone) have significantly reduced emesis but not nausea. Recent randomized clinical trials have demonstrated that olanzapine may be an effective agent for the prevention and treatment of chemotherapy-induced nausea as well as emesis.