The amount of prostaglandin E2 in endoscopic biopsy specimens from the mucosa of the gastric corpus and antrum of 10 healthy volunteers and 8 patients with alcoholic cirrhosis (7 of whom had portal hypertension) was measured by radioimmunoassay. The mean prostaglandin E2 level in both corpus and antral mucosa was significantly lower in the cirrhotic patients (p less than 0.025). Release of prostaglandin E2 into the gastric cavity was also significantly less in the cirrhotic patients in the basal state (p less than 0.025) and in that of tetragastrin stimulation (4 micrograms/kg, s.c.; p less than 0.01). There was no significant difference in acid secretion between the two groups of subjects. The histologic findings of biopsy specimens showed no difference in the extent of chronic gastritis between the cirrhotic patients and healthy subjects. Therefore, this deficiency of prostaglandin E2 in the gastric mucosa of cirrhotic patients was not related to acid secretion or chronic gastritis.