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Background: To determine normal ranges of gastroesophageal reflux (GER) in the proximal esophagus, measured with continuous pH monitoring. Normal ranges in the distal esophagus have been published. Because esophageal pH monitoring is frequently performed in children with atypical manifestations such as chronic respiratory disease, and because one of the possible pathophysiologic mechanisms may be (micro-)aspiration, it may be relevant to establish normal ranges in the proximal esophagus. Methods: Twenty-four-hour pH monitoring was performed in 200 children with suspected GER disease. The mean age of the patients was 4.5 months (range, 0.5–17.0 months). After initial analysis, patients were divided into three groups according to the reflux index (RI) in the distal esophagus, because it could be speculated that the amount of reflux reaching the proximal esophagus depends on the amount of reflux in the distal esophagus: Group I (n:120) children had a distal RI of less than 5% and were considered normal, group II (n:50) had a distal RI of 5% to 10% and was considered to have intermediate disease, and group III (n:30) had a distal RI of more than 10% and was regarded as pathologic. The following parameters are calculated: the RI, the total number of reflux episodes, the number of reflux episodes lasting more than 5 minutes, the duration of the longest reflux episode, and the acid clearance time (ACT). Results: The median RI in the distal esophagus was 3.8 ± 0.34 (standard error of the mean [SEM]), and in the proximal esophagus, the RI was 1.2 ± 0.23. In group I patients, the RI in the proximal esophagus was 0.5% ± 0.09%, in group II the RI increased significantly to 2.75% ± 0.34% (P [group I compared with group II] < 0.01), and in group III the RI was 6.15% ± 0.96% (P [II-III] < 0.01). The number of acid reflux episodes in group I was 17.0 ± 2.27, in group II the number increased to 62.5 ± 8.18 (P [I-II] < 0.01), and in group III it reached 102.0 ± 23.9 (P [II-III] < 0.05). Also the duration of the longest reflux episodes and the number of reflux episodes lasting more than 5 minutes increased from group I to group II, and from group II to group III. The ACT was shorter in the proximal esophagus (group I 0.3 ± 0.06 minutes; group II 0.48 ± 0.07 minutes, P [I-II] = not significant [NS]; group III 0.56 ± 0.17 minutes P [II-III] = NS) than in the distal esophagus (group I 0.49 ± 0.03 minutes, P [proximal ACT compared with distal ACT] < 0.05; Group II 0.76 ± 0.05 minutes, P [proximal-distal] < 0.01; Group III 0.89 ± 0.09 minutes, P [proximal-distal] = NS) suggesting more effective esophageal clearance in the proximal esophagus. Conclusions: Protection of the proximal esophagus from acid reflux is significantly related to the incidence and duration of reflux measured in the distal esophagus. These normal ranges in the upper esophagus will be helpful in the interpretation of upper esophageal pH monitoring data.