BACKGROUND: There is a group of patients who have unexplained chronic nausea and/or vomiting. In the past these patients were labelled as having psychogenic vomiting. However, there is little evidence that such a condition exists. Rather, these patients usually have a functional gastrointestinal disorder (functional nausea and vomiting). OBJECTIVE: This article describes the three important syndromes in adults that clinicians need to recognise: cyclic vomiting syndrome, functional vomiting, and chronic idiopathic nausea. DISCUSSION: Cyclic vomiting syndrome presents with stereotypical episodes of acute nausea and vomiting that may be severe. Patients are generally well between attacks. Cannabis use can cause a similar syndrome. Patients may respond to antimigraine therapy or low dose tricyclic antidepressant treatment. Functional vomiting is rare and presents with more frequent vomiting episodes. Rumination needs to be distinguished from functional vomiting by careful history taking. Tricyclic antidepressants are also useful in functional vomiting whether or not there is associated depression. Chronic idiopathic nausea refers to patients with bothersome nausea occurring several times a week usually not associated with vomiting. Its treatment is poorly defined but a trial of antidepressant therapy anecdotally can be helpful.