We made continuous, simultaneous recordings of esophageal pH from three sites in the esophageal body, for 18-24 h, in 11 children with normal prolonged distal esophageal pH studies (Group I) and in 14 children with abnormal distal esophageal pH recordings (Group II). A flexible catheter housing four antimony microelectrodes was used, and data were stored in a portable recorder. A computer allowed for evaluation of the percent of time esophageal pH was less than 4.0, number of reflux episodes per hour, acid clearance time, and the duration of longest reflux episode. Recordings made while subjects were upright or recumbent could be distinguished and analyzed separately. In the recumbent position, comparison of pH recordings from distal, middle, and proximal esophageal pH electrodes in Group I showed significant decreases in the percent of time spent with pH less than 4.0, reflux episodes per hour, acid clearance time, and duration of longest reflux episode in the proximal esophageal sites, with a near negligible total acid exposure in the most proximal electrode. In Group II subjects, however, comparison of recumbent recordings from distal, middle, and proximal esophagus indicates that the proximal esophagus is highly exposed to acid reflux and that the decrease in acid exposure from distal to proximal esophagus in reflux patients is not proportionally as great as that of Group I. The data suggest that in the recumbent position, the ability of the subjects with abnormal reflux scores to protect the upper esophagus is less than that of subjects with normal amounts of distal esophageal acid exposure.