The influence of the renin-angiotensin system on renal autoregulation and intrarenal distribution of blood flow was studied in 10 dogs. Using a femoral-renal bypass, total renal blood flow and perfusion pressure were determined under basal conditions and after graded renal arterial constriction. At each pressure level renal venous renin activity and the distribution of renal blood flow (Xe133-washout technique) were determined. In 4 dogs these studies were done after renin depletion by high sodium intake and injections of DOCA. Renal autoregulation of blood flow was abolished in renin-depleted animals. During reduction of renal perfusion pressure in the lower autoregulatory range or below, a redistribution of intrarenal perfusion could be observed from outer cortical to inner cortical-juxtamedullary compartments. The redistribution was more pronounced in renin-depleted than in normal animals. In normal dogs, reduction of perfusion pressure resulted in an increase in outer cortical perfusion rate as long as autoregulation was preserved. In renin-depleted animals, outer cortical perfusion rate decreased in proportion to pressure reduction. It is concluded that renal autoregulation of blood flow involves two mechanisms: one located in the outer cortical area under the influence of the renin-angiotensin system, the other located in the juxtamedullary compartment and independent of the renin-angiotensin system.