Eight dogs with cirrhotic portal hypertension were investigated for hemorrheology and hepatic hemodynamics. The whole-blood viscosity decreased in dogs with liver cirrhosis. The decrease in hematocrit may be responsible for low blood viscosity in cirrhosis. It was also found that the increase in portal venous resistance in cirrhosis was related to the anatomical changes of portal venous bed, but not to blood viscosity. Moreover, our experimental results indicated that raising blood viscosity might be one of the important measures for the treatment of esophageal variceal hemorrhage and for the prevention of rebleeding.