Literature related to the prevalence and etiology of anticipatory nausea and vomiting associated with chemotherapy is reviewed. Physiologic causes and psychological factors, including expectations, beliefs, and conditioning, are examined to help explain these phenomena. The efficacy of pharmacologic and behavioral treatments is discussed. Similarities between the experience of anticipatory nausea and vomiting and morning sickness suggest that the conditioning model may be relevant to understanding the development of pregnancy-related nausea.