Gastric emptying was measured using a modification of the double-sampling dye dilution technique in 16 children with gastroesophageal reflux and partial thoracic stomach (hiatal hernia), 13 with reflux per se, and 12 controls with nonspecific vomiting. No differences could be demonstrated between the rate of emptying in these groups. Our study failed to provide a rational explanation for the copious projectile vomiting that is a frequent manifestation of these disorders.