Among the many explanations of the cause of pancreatitis, the one attributing the condition to a reflux of bile into the pancreatic duct has seemed the most plausible to the greatest number of clinicians and surgeons. The reason for this is probably that the process, seemingly, may take place in man and that it deals with factors concerning which physicians are already acquainted. We have approached the problem of bile as the causative factor in acute and chronic pancreatitis from two aspects, the anatomic and the experimental. The investigation of the problem was suggested several years ago by Dr. E. S. Judd, and during the last six years the condition of pancreatitis has been studied in its general aspects, and several lines of investigation with regard to the most plausible features have been followed. In this article only the possible relation of bile to pancreatitis will be considered. The results