This series consists of 141 patients in whom cardiac mucosa (CM) was present in biopsy samples from the gastroesophageal junctional region. Inflammation of CM, irrespective of its exact anatomic location, was defined as carditis and classified as acute or chronic based on the number of inflammatory cells present. In all cases, CM showed significant chronic inflammation. One hundred and eleven (79%) of the 141 patients with carditis showed no evidence of gastritis in biopsy samples from the gastric antrum and body. Helicobacter pylori was present in 20 of 141 (14%) patients; of these, 17 had evidence of a pangastritis, with 15 of these patients also showing H. pylori in CM. Patients with severe chronic inflammation in CM had a significantly higher acid exposure of the lower esophagus as quantitated by a 24-hour pH test than those with mild chronic inflammation in CM. Acute inflammation was uncommon in CM; it was present in only 26 of 141 (18.4%) patients. There was no significant difference in acid exposure of the lower esophagus between patients with and without acute inflammation in CM. The presence of acute inflammation in CM was significantly associated with distal gastritis and H. pylori infection. Men with carditis had quantitatively higher acid exposure of the lower esophagus than did women with this disorder. This difference was greatest in men with severe inflammation in CM who had no evidence of distal gastritis. These findings provide evidence that chronic inflammation in CM is strongly associated with acid reflux and that H. pylori is not a significant etiologic factor in carditis. They also show that in patients with CM in whom H. pylori gastritis develops, the infection frequently spreads to involve CM, resulting in acute inflammation with neutrophils that is superimposed on the chronic inflammation already present.