THE EXISTENCE of more than one peptic enzyme in mammalian gastric juice has been suspected by several groups of workers. The evidence for this was mainly indirect and based on the presence of more than one pH optimum, each supposed to represent a separate enzyme. The complete separation of two different peptic enzymes from human gastric juice by Richmond et al1 and of three pepsin-like enzymes from crude pork pepsin by Ryle and Porter2 established this for the first time in a more direct way. The correlation between the total peptic activity of the gastric juice and disease has received much attention in the past. The evidence for more than one enzyme has led us to the investigation of the possible relationship between these separate enzymes and gastric disease. For this purpose, it was necessary to develop a simple, reliable method for the separation of these enzymes from