Serum gastrin increased in patients with pernicious anaemia after a beef-meal, but decreased after an oral load of glucose, xylose or sodium chloride. 50 g of glucose and 25 or 75 g of xylose suppressed serum gastrin to approximately 40% of basal values at 60 min and were slightly more effective than 10 g of sodium chloride. There was no rise in beef-meal stimulated serum gastrin concentration in vagotomized patients and only a slight rise in two patients with duodenal ulcer when an oral dose of 10 g of sodium chloride was given together with the beef-meal. 25 g of xylose suppressed basal serum gastrin concentration significantly in six vagotomized patients. Nasal administration of small amounts of vasopressin decreased basal serum gastrin significantly in six vagotomized patients. Nasal administration of small amounts of vasopressin decreased basal serum gastrin significantly in all subjects examined. Further studies indicated, however, that vasopressin was only effective when pharmacological plasma concenten orally and intraduodenally were compared in six patients with pernicious anaemia. Serum gastrin concentration decreased approximately to the same extent in both experiments. It is concluded that the inhibitory effect of glucose on gastrin secretion most likely is mediated hormonally via osmo-receptors located in the small intestine.