Gastric secretion was studied in two groups of rats in which pyloric ligature was made according to Dai's method. Both groups were put in a hypopressure chamber. One of the groups was normovolemic. The other group was made hypovolemic by acute bleeding. The following parameters were checked in gastire contents: volumen, acid and pepsin secretion, U.P./g. of stomach, chloride, potassium and sodium; in gastric mucosa total U.P. and pepsinogen concentration were measured. In the rats subjected to acute hypovolemia and hypoxia it was found a significant decrease in acid secretion, chloride and potassium mEq/1; there were no statistically significant changes in volume, pepsin secretion; U.P./g. of stomach and sodium mEq/1. Total U. P. and U.P./. of stomach increased in the gastirc mucosa.