Arterialization of the portal venous system was produced in 25 dogs by a prosthetic graft from the aorta to the proximal stump of the portal vein, after completion of an end-to-side portacaval shunt. Pressures and flows were measured. The reduction in total liver flow that follows a portacaval shunt was aggravated by an immediate 15% to 50% decrease in hepatic artery flow. There was a gradual increase in hepatic artery flow up to the fifth postoperative day. After arterialization of the portal system, the flow through the aorta-portal graft remained constant throughout an 80-day follow-up period. The 68% (17) of the dogs that survived the procedure were those in which the total liver flow was restored approximately to preoperative levels.