A preliminary report is presented regarding the 24 hours continuous pH monitoring of 40 patients from 1 month to 19 years of age with clinical features of gastro-esophageal reflux confirmed by at least one of the diagnostic methods utilized (radiology, endoscopy, esophageal biopsy). The equipment used was a MIC GASTROGRAPH with 1.2 and 3 mm catheters according to age and using the methodology suggested by ESPGAN. Patients with reflux index of more than 10% had all other pH indexes and other diagnostic methods abnormal. The area of the curve below pH 4 correlated directly with the presence of esophagitis. Patients with post history of esophageal atresia and caustic esophagitis had marked alterations of pH. PH monitoring with the modern methodology currently available is of great help to quantify severity of acid reflux, to distinguish between physiologic pathologic reflux and to decide treatment.