We report a meta-analysis of a series of studies in which 24-hour ambulatory pH monitoring was performed in 1) normal subjects, 2) the normal control subjects in studies of laryngopharyngeal reflux (LPR), and 3) the patients with LPR in these controlled studies. The statistical analysis utilized the fixed-effects model by Mantel-Haenszel and the random-effects mixed model. There were 16 studies from the past 12 years that fulfilled the inclusion criteria. They involved 793 subjects (264 normal and 529 with LPR). The numbers of positive pharyngeal reflux events for normal subjects and for patients with LPR differed with a p value of <.0001. There was also a significant difference in the mean percentage of acid exposure times between normal subjects and patients with LPR (p = .003). We conclude that the upper probe gives accurate and consistent information in normal subjects and patients with LPR. The numbers of reflux events and acid exposure times are most important in distinguishing normal subjects from patients with LPR. The technology and methodology of probe testing is quite reliable and is consistent on a worldwide basis.