1. Adrenocorticotrophic hormone-suppressed, bilaterally nephrectomized male mongrel dogs (n = 12) were infused with Sar1-angiotensin II and Asp1-angiotensin II, the naturally occurring octapeptide.
2. Sar1-angiotensin II was found to be almost twice as potent as Asp1-angiotensin II in elevating blood pressure but its aldosterone-stimulating activity was not higher than that of the naturally occurring peptide.
3. A specific competitive antagonist of angiotensin II, Sar1-Ile8-angiotensin II, blocked the pressor but not the aldosterone-stimulating activity of Sar1-angiotensin II.
4. These results suggest functional differences in receptors for angiotensin II in vascular smooth muscle and in adrenal cortex.