The role of AII receptors subtypes, AT₁ and AT₂, in the regulation of aldosterone secretion was studied in adrenal glomerulosa cells and membranes from rats on normal and low sodium intake, using AII receptor subtype-specific antagonists. In adrenal glomerulosa cells, more than 90% of the receptors were AT₁ and there was a good correlation between the potencies of the antagonists to inhibit ligand binding, and AII-stimulated aldosterone production and inositol phosphate formation. The inhibition of basal and ACTH-stimulated cAMP by AII was also abolished by the AT₁, but not the AT₂, antagonist. Sodium restriction for 6 days increased both receptor subtypes in the same proportion, but only the AT₁ antagonist inhibited AII-stimulated aldosterone production. The data demonstrate that AT₁ receptor mediates the regulatory actions of AII in the adrenal zona glomerulosa.