AIM: To assess the occurrence of gastric acid reflux into the esophagus in endoscopically confirmed prolapse gastropathy syndrome (PGS). METHODS: Using ambulatory esophageal pH measurement (BRAVOTM wireless esophageal pH monitoring system), twenty-six patients with PGS were compared with twenty-one patients with erosive esophagitis (EE) as controls. We assessed several reflux parameters, including the percentage of total time at pH＜4, and the DeMeester score. RESULTS: There were no statistical differences between the PGS group and the EE group as to mean age, sex ratio and pH recording time. The EE group showed more severe reflux than the PGS group, as evaluated in terms of the longest duration of reflux, the number of reflux episodes, the number of reflux episodes lasting＞5 min, the total time with pH＜4during acid reflux episodes, and the DeMeester score, but none of these parameters showed statistically significant difference. Although 53. 8% (14/26) of the PGS group and 76. 2% (16/21) of the EE group demonstrated pathologic acid reflux (DeMeester score＞14. 72), there was no statistically significant difference between the two groups in the incidence of pathologic acid reflux (P=0. 11). CONCLUSION: There was no statistically significant difference in pathologic acid reflux between the PGS and EE group. These data suggest that endoscopically diagnosed PGS might be a predictor of pathologic acid reflux.