Heartburn is a readily recognised symptom which half the British population have experienced at some time, and a fifth have frequently. It is the predominant symptom of gastro-oesophageal reflux, although less than two thirds of sufferers have endoscopically visible oesophagitis. Heartburn can also be associated with peptic ulcers or functional dyspepsia. Several changes in oesophageal function contribute to the syndrome of gastro-oesophageal reflux, the most important being inadequacy of the complex mechanism at the gastro-oesophageal junction. Understanding the various functional failures offers a better understanding of the therapeutic possibilities.