Serum gastrin determinations were performed in 32 normal-term infants to determine the level of this hormone in normal infants at birth and its response to normal feeding. Significant differences were noted between newborn cord blood and maternal blood at birth. Further significant elevations in fasting serum gastrins were noted in these infants over the first 72 hr of life. Pre- and postprandial determinations with normal feeding failed to demonstrate a significant elevation in serum gastrin levels following ingestion of protein-containing formulas. These data suggest a relative insensitivity of the release of gastrin from the gastric antrum in response to protein, a powerful mediator of gastrin release in the adult.