It has been suggested that endoscopic grading of the gastroesophageal flap valve is a good predictor of the reflux status. To test this hypothesis, 268 symptomatic patients underwent endoscopic grading of the gastroesophageal valve using Hill's classification, with grades I through IV. Esophageal acid exposure, lower esophageal sphincter characteristics, and the degree of esophageal mucosal injury were compared among the groups. The prevalence of a mechanically defective sphincter, abnormal esophageal acid exposure, erosive esophagitis, and Barrett's esophagus increased with increasing alteration of the gastroesophageal valve. The presence of a grade IV valve indicated increased esophageal acid exposure in 75% of patients. As a predictor, this is similar to lower esophageal sphincter pressure but not as good as the presence of esophageal mucosal injury. Endoscopic grading of the gastroesophageal valve provides useful information about the reflux status but is less useful as an indicator of gastroesophageal reflux disease (GERD) than the presence of esophageal mucosal injury.