BACKGROUND/AIMS: Pharyngeal pH monitoring at pH 4 is a cardinal diagnostic method for assessing laryngopharyngeal reflux (LPR). However, it has recently been suggested that weak acidic reflux above pH 4 may have a role in the development of laryngopharyngeal symptoms and mucosal damage. The aim of this study was to quantify the pharyngeal pH 5 reflux episodes and compare them with the pH 4 reflux episodes. METHODS: Thirty healthy subjects were studied using ambulatory 24-hour pharyngeal pH monitoring with glass electrodes positioned 1 cm above the upper esophageal sphincter and 5 cm above the lower esophageal sphincter. RESULTS: Of the healthy volunteers, LPR events occurred in 46.7% at pH 4 and in 86.6% at pH 5. After exclusion of mealtimes, the 95th and 90th percentile values for the percent of time the pH was<4 and that when the pH was <5 were 0.41, 0.18, 3.3, and 2.1, respectively. The 95th and 90th percentile values for the number of pharyngeal pH 4 and pH 5 reflux episodes were 12.8, 5.0, 16.5, and 14.5, respectively. CONCLUSIONS: Pharyngeal acid reflux episodes at pH 5 are present in most healthy adults. The present study provides prerequisite data for the evaluation of the etiologic role of the weakly acidic LPR for the occurrence of pharyngeal pathologic conditions in Koreans.