Gastric secretory dose-response studies, using an 8.5% mixed L-amino acid solution as the agonist, were carried out in three dogs with Heidenhain pouches and gastric fistulae. Secretory responses of the Heidenhain pouches were measured during two hour infusions of amino acids given at rates of 0, 0.05, 0.1, 0.2, 0.4, 0.8, and 1.6 g/kg/h and plasma amino nitrogen was measured before and during the infusion. Three separate studies at each dose level were made in each dog. The maximum secretory response occurred at the dose of 0.4 g/kg/h and amounted to approximately 20% of the maximal histamine response. Larger doses produced no additional increase in secretion or an actual decrease in secretory rate. It is concluded that the solution of amino acids used acts as a modest gastric agonist and that increases in plasma amino nitrogen such as may be observed after a protein meal are capable of eliciting a slight, but definite, gastric secretory response.