The purpose of this study was to investigate the rate of gastric emptying of a liquid meal in young children with symptomatic gastroesophageal reflux of varying intensity. Twenty-three infants (mean age 7.0 +/- 1.4 [SEM] months, range 2 to 14 months) were evaluated for reflux by esophageal manometry, a five-hour pH probe study, and barium swallow. The rate of gastric emptying was determined by using a liquid meal of 4 ounces of cow milk formula labeled with 99mTc sulfur colloid. In seven infants with failure to thrive and objective criteria for severe reflux, the mean gastric emptying was 21.3 +/- 6.4% at one hour. In six infants with reflux and recurrent pulmonary disease, the mean gastric emptying was 19.8 +/- 5.4%. Ten infants with mild reflux, adequate weight gain, and no pulmonary symptoms emptied 44.3 +/- 6.0% of formula at one hour, and six normal adults (mean age 28.3 +/- 2 years) emptied 56.2 +/- 6.5% of formula at one hour. These data suggest that infants with severe GER have significantly delayed gastric emptying, that gastric retention may contribute to the FTT and pulmonary symptoms in these infants, and that abnormal motor function of the gastric fundus may be a significant factor in the pathogenesis of gastroesophageal reflux of infancy.