SUMMARY1. Although gastrin is found in adult gastric juice, rapid enzymatic destruction by pepsin in the acid environment makes a physiological role in the adult unlikely.2. Gastric pH in the fetal sheep is neutral so that gastric juice gastrin could be present, and if present, have a physiological function.3. The aim of this study was to determine the presence, molecular forms and metabolism of gastrin in gastric juice.4. Gastrin was present in fetal gastric juice at significantly higher concentrations than in fetal plasma.5. The majority of gastric juice gastrin was present as the biologically active gastrin‐17.6. Gastrin was stable in normal fetal gastric juice, but was rapidly metabolized to smaller C‐terminal fragments when the gastric juice was acidified.7. With the known growth promoting effect of gastrin on gastrointestinal mucosa, gastrin in fetal juice could have a unique role in thein uterodevelopment of the gastrointestinal tr