Applications of an ultrasonic duplex system on measurement of the hepatic circulation, especially of the portal circulation have been developed. Portal blood flow can be calculated from the cross-sectional area and the mean blood flow velocity. In patients with portal hypertension, the cross-sectional area of the portal vein is larger than normal, and the blood flow velocity of the portal vein is lower than normal. However, the blood flow volume of the portal vein is well maintained in portal hypertensive patients in spite of development of the porto-systemic collateral pathways. We called the ratio of the cross-sectional area to the blood flow velocity of the portal vein the "Congestion Index (C.I.)" of tne portal vein. In portal hypertensive patients, the C.I. value is significantly larger than normal. The portal vascular resistance can be calculated from the portal perfusion pressure and the portal blood flow, both of which are measured simultaneously and percutaneously. The measurement of the portal vascular resistance is useful for diagnosis of pathophysiology of the hepatic hemodynamics.