THE PRESENT study is the outgrowth of attempts to produce a form of portal hypertension in the dog which is consistent with that seen in man. It was observed that chronic occlusion of the portal vein in the dog did not result in a consistent elevation of the portal venous pressure. These initial studies were made in unanesthetized animals with pressures taken through a No. 19 needle inserted via a previously placed London cannula. It was found that nearly complete occlusion was required before a significant elevation of portal pressure could be produced in the acute preparation. Gradual occlusion over a two- to three-week period stimulated sufficient collateral circulation to allow complete occlusion without death of the animal. These studies were confirmed in the report before this meeting last year by Douglass, Mehn, Lounsbury, Swigert, and Tanturi.1 They have recently been again confirmed by Morris and Miller.2 Since