['To assess the diagnostic value of pH monitoring.', 'A prospective study.', 'Pediatric university hospital serving as a secondary and tertiary referral center.', 'Thirty-eight infants, aged 1 to 12 months, and 26 children, aged 13 months to 18 years, admitted during a 2-year period because of clinically significant gastroesophageal reflux (GER).', 'Prolonged (20-hour) pH monitoring as well as endoscopy and biopsy of the esophagus were carried out in all patients who, on the basis of clinical data, were classified as having mild, moderate, or severe GER disease.', 'In the infant group, results of prolonged pH monitoring were abnormal in 34 (89.5%). In the older group, results were abnormal in less than half (11 [42.3%]) of the cases. In both groups, pH monitoring data did not correlate with the severity of GER disease or of esophagitis. Severity of GER disease was not predictive of esophagitis.'] Is prolonged pH monitoring of limited usefulness for gastroesophageal reflux?