To measure the effect of a sliding (concentric) hiatus hernia on gastroesophageal sphincter competence, 75 patients were studied: 25 patients without esophageal symptoms and without hiatus hernia (Group A); 25 patients without esophageal symptoms but with hiatus hernia (Group B); and 25 patients with symptoms of severe gastroesophageal reflux, with or without a hiatus hernia (Group C). In Group C, 12 patients had a hiatus hernia, and 13 did not.