Five Labrador retrievers provided with one vagally innervated and one denervated pouch were given graded doses of food composed of liver, heart and bonemeal to make dose/response curves of food-stimulated gastric secretion. A constant ranitidine infusion resulted in a decreased inhibition of acid output as the physiological stimulation increased both in the innervated and in the denervated pouch. The pepsin output behaved quite differently. The increased physiological stimulation did not increase the pepsin output. There was no inhibition by ranitidine in the innervated pouch and a constant inhibition by ranitidine in the denervated pouch. The results indicated a component of competitive interaction between meal-stimulated acid secretion and the H2-receptor antagonist, which is similar to the interaction between H2-receptor antagonist and histamine.