Noradrenergic innervation of rat liver was studied immunohistochemically using antibody to noradrenaline at the electron-microscopic level. Noradrenaline-immunoreactive nerve fibres were located in the portal tract and some were in close contact with the portal vein and hepatic artery. Noradrenaline-immunoreactive fibres were found to contain many vesicles that were reactive to anti-noradrenaline antibody. This preliminary study suggests that the method for detecting noradrenaline-immunoreactive fibres using the antibody is useful for studies at the electron-microscopic level.