Nausea is an uneasy feeling in the stomach while vomiting refers to the forceful expulsion of gastric contents. Chronic nausea and vomiting represent a diverse array of disorders defined by 4 weeks or more of symptoms. Chronic nausea and vomiting result from a variety of pathophysiological processes, involving gastrointestinal and non-gastrointestinal causes. The prevalence of chronic nausea and vomiting is unclear, although the epidemiology of specific conditions, such as gastroparesis and cyclic vomiting syndrome, is better understood. The economic impact of chronic nausea and vomiting and effects on quality of life are substantial. The initial diagnostic evaluation involves distinguishing gastrointestinal causes of chronic nausea and vomiting (e.g., gastroparesis, cyclic vomiting syndrome) from non-gastrointestinal causes (e.g., medications, vestibular, and neurologic disorders). After excluding anatomic, mechanical and biochemical causes of chronic nausea and vomiting, gastrointestinal causes can be grouped into two broad categories based on the finding of delayed, or normal, gastric emptying. Non-gastrointestinal disorders can also cause chronic nausea and vomiting. As a validated treatment algorithm for chronic nausea and vomiting does not exist, treatment should be based on a thoughtful discussion of benefits, side effects, and costs. The objective of this monograph is to review the evaluation and treatment of patients with chronic nausea and vomiting, emphasizing common gastrointestinal causes.