The aim of this prospective work was to analyze the results of 3 methods of esophageal pH recording (i. e. short-term pH test, 3-hr postprandial recordings, and 12-hr nocturnal pH recording) in 47 patients with suspected gastroesophageal reflux. Nocturnal pH recording was used as a reference for evaluation of the diagnostic value of the 2 other pH tests. Normal ranges were established from 20 control subjects. Esophageal endoscopy with biopsies were performed systematically in order to evaluate the relationship between pH results and the grades of esophagitis. According to the results of nocturnal pH recordings, 32 patients were considered to suffer from acid gastroesophageal reflux and 15 patients as being free of reflux. The sensitivity and specificity of the pH measurements were 0.94 and 0.13 for the short-term pH test and 0.91 and 0.80 for 3-hr postprandial recordings respectively. The total duration of reflux (expressed as a percentage of total duration of the test) was the most discriminative parameter for the diagnosis of reflux and was simpler to determine than previously described pH scores. Because of the absence of lamina propria in the biopsy specimens obtained at endoscopy, histological diagnosis of esophagitis was possible in only 35 patients (74 p. 100). No relationship was found between the grade of esophagitis and the results of short-term pH tests. On the other hand, the mean duration of reflux episodes, the duration of the longest episode, the total duration of reflux measured by 12-hr nocturnal pH recording, and the number of low pH reflux episodes determined by postprandial tests were significantly higher in patients with macroscopic lesions than in those with normal endoscopic aspect or mild (histological) lesions of esophagitis.(ABSTRACT TRUNCATED AT 250 WORDS)