The tolerability of chemotherapy has been significantly improved by the advent of effective drugs and protocols for the amelioration of chemotherapy-induced nausea and vomiting. Variables such as the timing of nausea and vomiting (acute, delayed or anticipatory) and the emetogenicity of the chemotherapy must be taken into account in developing guidelines for antiemetic prophylaxis and treatment. Although there are a number of 5-hydroxytryptamine antagonists available, the clinical differences between them are small. The use of drugs with a different mechanism of action, such as the recently introduced neurokinin-1 receptor antagonist aprepitant, may be a useful adjunct to 5-hydroxytryptamine-3 receptor antagonists or steroid prophylaxis. The addition of aprepitant to standard antiemetic regimens increases the proportion of complete responses to antiemetic therapy. For the use of highly emetogenic chemotherapy in oncology a combination of 5-hydroxytryptamine-3 receptor antagonist, dexamethasone and aprepitant is recommended in the acute phase, and dexamethasone plus aprepitant during the subsequent days (many patients do not have their symptoms controlled by 5-hydroxytryptamine-3 receptor antagonist and steroid alone). In either case, lorazepam can be added as required. For moderately emetogenic chemotherapy, a regimen of 5-hydroxytryptamine, dexamethasone and aprepitant is recommended in the acute phase, followed by aprepitant alone in the delayed phase. Alternatively, a 5-hydroxytryptamine-3 receptor antagonist and dexamethasone can be used in the acute phase, followed by dexamethasone for prophylaxis in the delayed phase. For chemotherapy with a low emetogenicity, either dexamethasone, metoclopramide, prochlorperazine or triethyperazine alone is recommended. No prophylaxis is generally required during the delayed phase and indeed may not be necessary during the acute phase either.