The inadequacy of the titrametric method for measuring gastric acidity with Töpfer reagent as indicator for the study of gastric anacidity in the intact stomach has been emphasized previously.1More recently2this inadequacy has been shown to be perhaps even greater if the method is used to evaluate the effect of subtotal gastrectomy on the secretion of the remaining gastric pouch. In both of these studies we found the determination of hydrogen ion concentration of the gastric contents to be the most precise method for establishing the true status of gastric acidity when no titratable free acid is present. It is vital for the ulcer patient who has had a subtotal gastric resection to develop an anacidity in the remaining gastric pouch if he is to be safeguarded against the development of new ulcers. We believe that it is important to study gastric secretion in these patients very