To gain insight into generating and transport mechanisms of angiotensin (ANG) in the brain the study was focused on the subcellular localization of ANG II and its AT(1)-receptors in the hypothalamus of rats. The present paper demonstrates ANG II- and AT(1)-receptor-immunolabelling at brain parenchyma vessels and at glial and neuronal structures in the perivascular region. Further, ANG II- and AT(1)-receptor-immunoreactivity is shown at plasma membranes and intracellular structures in the ependyma of the third ventricle. Based upon a conventional horseradish peroxidase technique, combined with the classical substrate 3,3'-diaminobenzidine, a procedure is introduced that will be useful with a variety of antibodies used on glutar- and paraformaldehyde-fixed brain tissue. This technique enables a fast correlation between light and electron microscopical results and might also provide an attractive alternative to colloidal gold-labelling and silver-intensification techniques.