Abstract: Objective: To determine the postprandial acid distributions in patients with gastroesophageal reflux disease (GERD), and their relationship with esophageal acid exposure. Methods: Esophageal and gastric pH were recorded in a 1h fasting segment and a 4h postprandial segments using a triple-channel pH catheter with three antimony electrodes, which were positioned 5cm proximal to the upper margin of LES(LES-5cm), 5cm and 10cm distal to the upper margin of LES(LES+5cm and LES+10cm), respectively. Esophageal acid exposure and gastric integrated acidity (IA) were calculated for each ambulatory pH study. Ten healthy subjects (HS) and 10 patients with GERD were enrolled. Results: (1) Total postprandial IA had a trend to be lower at LES+5cm than at LES+10cm in HS, but there was no significant difference between the two positions in patients with GERD. (2) At 2nd hour after meal, there was no significant difference of gastric IAs between 2nd hour after meal and baseline in HS. Whereas gastric IAs in patients with GERD recovered to a higher level than baseline: LES+5cm: 5.4 (1.8-6.8) mmol/Loh vs. 1.8(0.3-3.1) mmol/Loh (P <0.05); LES+10cm: 5.6(2.4-7.6) mmol/Loh vs. 2.3(0.8-3.1) mmol/Loh, (P=0.05). (3) Excessive esophageal acid exposure occurred mainly at 2nd hour after meal both in HS and the patients, but were higher in patients than in HS. There was no statistically significant relationship between esophageal acid exposure and gastric IA on each postprandial segment in the patients with GERD and HS. Conclusion: The present study suggested that abnormal acid distribution in proximal stomach and an enhanced meal stimulated acid secretion may partly elucidates excessive postprandial esophageal acid exposure in patients with GERD.