VON ECK1 first produced a portacaval fistula in dogs in 1877, and he performed eight such operations. In this operation the portal vein was ligated between the anastomosis and the liver. Other reports since this time by Pavlov,2 Freeman3 and others have indicated that a fistula produced in this manner will remain patent. In our hands the production of such a fistula in the dog without portal obstruction results in closure of the fistula in approximately one third of the cases in three to six weeks. It seemed important to produce chronic portal hypertension in dogs to determine whether a similar frequency of closure occurred in the portacaval fistulas before applying the procedure to human beings. Chronic portal hypertension has been produced by Kershner, Hooton and Shearer4 in the dog by partial obstruction of the inferior vena cava. This procedure was not applicable in our experiments,