In a group of six dogs with Heidenhain pouches, the infusion of a solution of L-amino acids caused identical increases in gastric secretion when given into the jejunum as when administered directly into the portal venous system. Elevations in plasma amino nitrogen were also similar in the two circumstances. In four dogs with Heidenhain pouches and portacaval transposition, a similar infusion caused an identical increase in gastric secretion when given into the jejunum as when given into the peripheral venous system; plasma amino nitrogen levels were almost as high with the jejunal administration as with venous infusion. It is concluded that all, or almost all, of the gastric secretion evoked by amino acids in the canine intestine can be accounted for by the direct effect of absorbed amino acids on parietal cell secretion, with little or no contribution from release of an intestinal hormone.