A controlled, prospective comparison of the use of the infant seat versus prone, head-elevated positioning in a harness was undertaken in 15 infants with gastroesophageal reflux. pH monitoring of the distal esophagus demonstrated less reflux in the harness than in the seat (P less than 0.001) during 19 pairs of two-hour postprandial trials. This difference was the result of both fewer episodes (P less than 0.001) and briefer episodes (P less than 0.05). Prone-elevated positioning in the harness described is superior to positioning in an infant seat in the treatment of gastroesophageal reflux in infants younger than 6 months.