The role of osmolar load in the regulation of gastric emptying time was studied in 10 healthy premature infants. Two isocaloric infant feedings of similar composition with mean osmolalities of 279 and 448 mOsm/kg were compared. Emptying was studied over 120 min by the double sampling marker dilution technique and by a single aspiration of the feeding at 30 min. Similar gastric emptying times were noted for both formulas with approximately half of the initial gastric contents remaining at 30 min. The secretory response to the two meals during the first 30 min after feeding was compared by measuring the secretions present in the stomach during that time. The mean secretory response to the feedings did not differ significantly and was less than 2.5 ml in both cases. In general, a biphasic pattern of gastric emptying with a rapid early emptying phase was noted with both feedings. This study, therefore, provides evidence that when isocaloric feedings with similar composition are used, osmolar load does not play a significant role in the regulation of gastric emptying in premature infants. This study also demonstrates that differences in osmolality do not significantly affect the secretory response to a meal in the stomach of the premature infant.