The responses of amylase and chymotrypsinogen to a pancreatic secretory stimulation (intragastric administration of oleic acid or sodium oleate) are compared in rats. This comparison concerned the rates of biosynthesis of the two enzymes, their intrapancreatic levels of storage and their rates of excretion in the juice. In each of these 3 steps, it was found that the stimulation induced non-parallel courses of amylase and chymotrypsinogen. The non-parallelism in the rates of biosynthesis was found unable to explain the entire non-parallelism observed in the rates of excretion. These results suggest that the mechanism which controls the proportions of the different enzymes in the juice is different from that which monitors the rates of individual enzymes biosynthesis.