AbstractSpecific binding sites for angiotensin II were localized in the developing rat kidney (18th day of pregnancy and immediately before birth) by autoradiography using [125I]‐ileu‐5‐angiotensin II either perfusedin vivothrough the fetal aorta or addedin vitroto frozen sections in an incubation mixture. Specific binding was localized in the walls of the afferent and efferent arterioles, in the intraglomerular cells and in the peritubular arterioles of the subcapsular cortical zone. The immunohistochemical analysis, carried out on receptors saturated with unlabelled angiotensin II perfused through the mother's aorta, confirmed the autoradiographical localization. Antisera against ileu‐5‐angiotensin II were used in the indirect immunofluorescence technique and in the PAP method. Immunolocalization of angiotensin II was also found in the proximal tubule and in the thick ascending limb of Hen