Cyclic vomiting syndrome (CVS) consists of discrete episodes of nausea and vomiting lasting hours or days, separated by symptom-free intervals of similar or varying lengths. The disorder is not caused by underlying organic disease. The episodes tend to be similar in time of onset, duration, and symptomatology specific for each patient and are self-limited. The majority of patients can identify experiences or conditions that may precipitate episodes, the commonest being heightened emotional states and infections. The onset of CVS most often occurs during preschool or early school years, although it may begin at any age, from infancy to mature adulthood. CVS episodes can recur for months or decades, and their subsidence cannot be predicted.