Following previous observations that medium chain triglycerides (MCT) are absorbed from the stomach of suckling rats, this study was devoted to studying absorption of MCTs in human infants. Four groups of patients were studied: (a) infants suffering from pyloric stenosis, (b) premature infants, (c) children suffering from cystic fibrosis, (d) infants with miscellaneous conditions. Infant formulae with known amounts of MCT were introduced by gastric tube and samples were removed at 0, 20, 40, and 60 min. In patients with pyloric stenosis there was an 18.1% decrease in MCT during the first 20 min. No significant changes in MCT took place during the subsequent 40 min. A similar response was observed in the group of premature infants. Older infants with miscellaneous diagnoses and children with cystic fibrosis showed an even rate of disappearance of MCT during the 60-min test period, and approximately 30% of the original MCTs present disappeared during this period. We conclude that MCTs are absorbed in the stomach of infants and children. Absorption appears to improve with age. Because MCT are an important constituent of formulae for premature infants and children with defects of small intestinal digestion and absorption of fat, these observations have practical implications.