Thirty-four infants with symptoms of gastroesophageal reflux were evaluated by esophageal manometry, pH probe, and gastric emptying studies. Infants with failure to thrive (group A) and recurrent pulmonary disease (group B) had more severe reflux by pH probe (41.6% and 36.3% reflux time postprandially, respectively) than the group of infants without serious sequellae of gastroesophageal reflux (group C), who had 19.0% reflux time postprandially, p less than 0.01. Lower esophageal sphincter pressure did not vary significantly between infants with severe reflux and milder disease. Groups A and B had significantly decreased peristaltic amplitude in the distal body of the esophagus (28.3 +/- 4.8 and 23.2 +/- 5.5 mmHg, respectively) when compared to group C (50.2 +/- 3.2 mm Hg, p less than 0.01); in addition to a significantly increased number of nonperistaltic sequences. Gastric emptying of isotope-labeled cow's milk formula after 1 h was 20.9% and 22.8% in groups A and B, respectively; significantly delayed compared to 40.6% of the meal emptied in group C infants. Gastric retention was significantly correlated with impaired distal esophageal peristaltic amplitude (r = 0.68) and increased postprandial pH documented reflux (r = 0.60). Our results provide evidence for the diffuse nature of the upper gastrointestinal motility disorder present in severe gastroesophageal reflux of infancy.