All physicians encounter patients who have symptoms that are difficult to treat because the mechanisms which produce them are poorly understood. Gastroenterologists deal with a number of such symptoms, among which may be listed not only the many varieties of abdominal pain but also such complaints as belching, flatulence, malodorous breath, a bad taste in the mouth, coated tongue and heartburn. Although these are usually considered to be of minor significance, they may cause great annoyance and, by their resistance to treatment, create troublesome problems for both the patient and the doctor. Heartburn, the subject of this discussion, is such a symptom of vague causation. Although much has been done to explain its origin, there still exists a need to evaluate the clinical significance of heartburn and of the factors which cause it, so that satisfactory therapy can be planned. The various studies already carried out in investigating the origin