Summary A method is described for implanting and maintaining cannulae in the central hepatic vein, the portal vein and a mesenteric vein in adult dairy cows. Blood flow rates in the hepatic and portal veins were measured using indicator dilution techniques. Hepatic venous blood flow rate was approximately 30 l/min (54 ml/min per kg body wt.) in a non-lactating cow. Starvation for 5 days caused this value to fall by about 40%.