Factors causing portal hypertension were investigated on cases of chronic hepatitis (type Ⅲ in peritoneoscopic classification), in which increased number and enlargement of small blood vessels on the liver surface were peritoneoscopically discernible and in which there were portal-hypertensive signs such as splenomegaly, enlarged vessels belonging to the range of portal vein. Three-dimensional observation on the hepatic blood circulation in hepatitis was performed by means of reconstruction of serial sections of liver tissues which were derived by hiopsy. 1. Narrowed vessels in the branches of portal vein below the 11th or 12th branch by Miyake were demonstrated in 14 out of 18 cases of chronic hepatitis with portal hypertension (43 out of 92 small branches of portal vein). On the other hand, such narrowing was observed only in 3 out of 13 cases without signs of portal hypertension. 2. In some cases, both narrowed branches and enlarged ones of portal vein were demonstrable on the same liver. Normal small branches were presumably enlarged in order to compensate the disturbad blood flow at the narrowed portions. In the Glisson's capsules with enlarged small branches of portal vein, there were few histological changes of fibrosis, cell infiltrations, etc.