Esophageal pH monitoring has been performed in 60 asymptomatic neonates between 1 and 10 days old. Several parameters (periods with a pH less than 4, number of reflux episodes, number of reflux episodes lasting more than 5 min, average duration of the longest reflux episode, average pH) were studied in different positions (in prone and supine position, in right and left side lying position). For all parameters, except for the average pH, we obtained significantly more favorable results in prone position. In 22 vomiting neonates, significantly favorable results were obtained only by application of positional therapy: in prone position with head elevated (anti-Trendelenburg). There was no significant difference between the symptomatic group (with radiologically proven reflux pathology) in prone and anti-Trendelenburg position, and the control group in prone horizontal position. The 17-h continuous pH monitoring in the newborn is a nonaggressive investigation technique in physiological circumstances, which adequately completes and/or replaces the traditional examinations on gastroesophageal reflux. This method enables an evaluation of the favorable effect of simple therapeutic means (positional changes). Medication, and thickening and staggering of feeding (a time-consuming and tiring burden for the parents), can be avoided with this technique.