Current concepts in physiology and pathophysiology of lower esophageal sphincteric mechanism are reviewed. With recent advances in manometric method for more accurate in-vivo human studies combined with in-vivo and in-vitro studies in animal models, there is much information regarding function of this sphincter. Three components of sphincter control have been identified: specialized circular smooth muscle at esophagogastric junction, autonomic nervous system, and probable physiology effects of gastrointestinal hormones, particularly gastrin. Clinical syndromes of sphincteric dysfunction have been identified relative to these three controlling elements. Foods and drugs that adversely effect sphincter pressure have been identified and indicate that anticholinergic agents, fatty foods, chocolate, alcohol, and cigarette smoking may have a harmful effect on a patient with heartburn. Drugs that increase the antireflux sphincter barrier have been studied. Clinical effectiveness of antacids and bethanechol in therapy of heartburn is supported by controlled treatment trials. Research continues on other medications producing increases in sphincter pressure.