['Detailed understanding of the functional anatomy of the lower esophageal sphincter (LES) is germane to successful surgical treatment of esophageal disorders. However, a comprehensive concept of the structure-function relationship of the LES is currently lacking.', 'We reviewed published anatomic evidence, medical imaging, and impedance manometry data sets and developed a novel functional concept of the LES.', 'Morphologic evidence accumulated over the past three decades indicates that the LES is an anatomic structure that differs markedly from typical ring sphincters of the gastrointestinal tract (e.g., upper esophageal sphincter or anal sphincters). Recent impedance manometry investigations shed new light on the functional anatomy of the LES. These data corroborate a concept of this sphincter as a double-layer, twisted stretch sphincter. This sphincter requires tissue tension for optimal function. Retightening of the longitudinal stretch of the esophagus provides an effective therapy if this tension is lost, e.g., for patients with hiatal hernias. Paralysis of the muscle fibers of this sphincter system results in functional obstruction, and this explains the pathophysiology of "achalasia".'] Do manometry data support a novel concept of the lower esophageal sphincter system?