The exact incidence of esophagitis in gastroesophageal reflux disease (GERD) remains poorly understood in Korea. To determine incidence of esophagitis in GERD, from August 1988 to July 1993, endoscopy, esophageal manometry with Bernstein test, and ambulatory 24 hour esophageal pH monitoring were carried out in a group of 349 patients with symptoms of heartburn or noncardiac chest pain. Based on these studies, 151(40%) patients had some degree of GERD and pstients were categorized as having: pathologic reflux, 98 patients; symptomatic reflux, 42 patients; and sensitive mucosal reflux, 11 patients. Among 151 patients with GERD, 27 patients(18%) had some degree of esophagitis. In conclusion, 40% of patients with symptoms suggestive of GERD have GERD. GERD is divided into subgroups; pathologic reflux, symptomatic reflux, and mucosal sensitive reflux. Less than 20% of GERD have esophagitis or esophageal mucosal injury and these low incidence of mucosal injury in Korean may be due to increased esophageal mucosal resistance.