The purpose of this study was to evaluate the possible role of the lung as an organ for inactivation of exogenous gastrin. Human synthetic gastrin was infused into the right and left atria of 4 mongrel dogs with Heidenhain pouches. The mean rate of acid secretion in response to right atrial gastrin infusion was 0.39 mEq/15 min, as compared to the mean rate of 0.36 mEq/15 min when the gastrin was infused via the left atrium. The difference in gastric acid secretory response to infusion of gastrin into the right or left atrium was not statistically significant.