Nausea is a subjective constellation of sensations that immediately herald vomiting, while vomiting is defined as the active retrograde expulsion of gastric contents through the mouth. The differential diagnosis of nausea and vomiting is extraordinarily broad, and includes: (i) disorders of the abdominal viscera, (ii) drug, toxin or other exposures, (iii) infection, (iv) central nervous system disease, (v) metabolic and endocrine disease and (vi) other miscellaneous causes. There is a lack of controlled trials to guide a diagnostic algorithm for nausea and vomiting; current recommendations are largely based on expert opinion with an evidence rating of C. Often, the history and physical examination will lead to the etiology of nausea and vomiting. Initial evaluation should to help determine or confirm the etiology of the symptoms and determine consequences of the symptoms, such as dehydration. Treatment should be directed at managing the underlying disease.