The sensitivity and specificity of each of five esophageal tests used in the diagnosis of reflux esophagitis were compared with those of six combinations of two tests, one indicating esophagitis and the other indicating sphincter incompetence. The esophageal tests were performed in patients with reflux symptoms, chest pain, and esophagitis without reflux symptoms. Control data were obtained from normal subjects (negative control) and duodenal ulcer patients (positive control). The results indicate that the acid infusion test and esophageal biopsy combined with esophageal pH study after HC1 have similar sensitivity and greater specificity than any test alone. In normal subjects, the cumulative incidence of abnormalities with esophageal tests alone was 30%, but with combinations of two tests it was only 5%. The use of criteria (simultaneous esophagitis and sphincter incompetence) which establish the diagnosis of reflux esophagitis helps to resolve conflicting results obtained with single tests. The most sensitive and specific test combination for the diagnosis of reflux esophagitis appears to be esophageal biopsy with esophageal pH study after HC1.