Plasma levels of glucagon, secretin, norepinephrine, arginine-vasopressin, and prostaglandin biosynthesis in the gastric mucosa were determined in cirrhotic patients with gastric vascular ectasia associated with hypoacidity, in cirrhotics without this lesion, and in healthy controls. Plasma concentrations of glucagon, secretin, and norepinephrine were similar in cirrhotics with gastric vascular ectasia and cirrhotics without this lesion, these concentrations being significantly higher (p less than 0.05) than in healthy controls. However, there was no significant difference between plasma levels of arginine-vasopressin in patients with cirrhosis (with or without gastric vascular ectasia) and those in healthy controls. The biosynthesis of prostaglandin E2 in the antrum of the gastric mucosa was significantly higher in cirrhotics with gastric vascular ectasia than in cirrhotics without this lesion (p less than 0.05) and healthy controls (p less than 0.005). Prostaglandin E2 in the corpus was significantly higher (p less than 0.05) in cirrhotics with gastric vascular ectasia than in healthy controls. The biosynthesis of 6-keto PGF1 alpha (a stable metabolite of prostacyclin) and PGF2 alpha in the corpus and antrum of gastric mucosa was not significantly different in cirrhotics with gastric vascular ectasia, cirrhotics without this lesion and healthy controls. Since prostaglandin E2 has a vasodilator and acid-inhibitory effect, we speculate that high content of this prostanoid in the gastric mucosa may play a role in the pathogenesis of ectatic capillaries and acid inhibition present in some cirrhotic patients.