The precise effect of portacaval shunt upon liver blood flow is still under discussion. In the present work, the consequences of portal-systemic shunt on hepatic blood flow were investigated in rats with normal liver. Hepatic blood flow was measured 24 h after a portacaval shunt according to the technique of constant Bromsulphalein infusion. There was no decrease of hepatic blood flow. Thus, at that time in the rat the increase in the hepatic arterial flow was able to totally compensate portal blood diversion, as opposed to what has been reported in the dog. It is suggested that extrapolation to man of previous work showing changes in blood flow in the dog should be reconsidered.