Dogs with chronic biliary cirrhosis and portal hypertension commonly develop plasma volume expansion, urinary sodium retention, ascites, and perturbed systemic hemodynamics, i.e., a rise in cardiac output and a fall in peripheral vascular resistance. Our laboratory has previously demonstrated that creating a side-side portacaval anastomosis in such animals, and so venting hepatoportal pressure, will prevent sodium retention and ascites formation and will maintain the animals euvolemic. In the present study, in four cirrhotic dogs with such an anastomosis, observations made at 12 weeks postbiliary duct ligation, and in the presence of grossly disturbed liver function and morphology, failed to demonstrate any change from control conditions in arterial blood pressure, cardiac output, or peripheral vascular resistance. We conclude that venting hepatoportal pressure in cirrhotic dogs with markedly disturbed liver function prevents the advent of a hyperdynamic circulation, possibly by preventing volume expansion.