• The junction of the esophagus and stomach is normally closed except during deglutition, but the structures and mechanics involved in the closure are poorly understood. Roentgenologic observations indicate that the lowermost segment of the esophagus, over a length of 2 to 4 cm., constitutes a functional internal sphincter and that the muscle bundles about the hiatus of the diaphragm constitute an external sphincter. Dislocation of these sphincters in the presence of a hiatal hernia may disturb the closing mechanism at the cardia and permit reflux of gastric juice into the esophagus. The ensuing peptic esophagitis causes most of the symptoms usually ascribed to the hiatal hernia. Further complications are acute lacerations at the esophagogastric junction with severe hemorrhage following vomiting, the peptic marginal ulcer sometimes converted from these lacerations by chronic peptic irritation, and slowly developing anemia. The close interrelation of these conditions to each other and to the disturbed sphincteric closure in the presence of a hiatal hernia is illustrated by roentgen observations, diagrams, and a report on a patient with fatal Mallory-Weiss lacerations.