A procedure for catheterization of a right hepatic vein is described in the rat. The procedure is based on the observation that, when the posterior half of the body is bent to the left, a right hepatic vein is aligned with the axis of anterior vena cava and posterior vena cava. A catheter, inserted in the right jugular vein and fitted with a rectilinear mandrel, is guided into the right auricle, the suprahepatic segment of posterior vena cava and a right hepatic vein. Successful catheterization of a right hepatic vein has been obtained in 47 out of 50 animals in which the procedure has been performed.