The hepatic circulation, which is essentially important in supplying liver cells with oxygen and substrates needed for securing metabolic homeostasis, is well regulated by extrahepatic and intrahepatic mechanisms. Autoregulation of hepatic artery flow, as well as pressure mediated vascular interactions between hepatic-arterial, portal venous and hepatovenous blood flow, secure a constant low pressure sinusoidal liver perfusion. Apart from these hemodynamic mechanisms, there are also specific morphologic features in the hepatic vascular bed responsible for regulating liver blood flow. Functional aspects concerning the arterial and portal venous contributions in liver circulation give strong evidence that portal blood may be of greater importance than arterial, especially for hepatic nutrition and trophics, as well as for metabolic homeostasis of the whole organism. In portacaval shunt operations, portal venous flow to the liver should be preserved to the greatest extent possible.