The renal microvasculature was examined stereoscopically after intraarterial injection of silicone rubber. Specimens studied were: 29 cases of normal kidney, 4 cases of sclerotic kidney, 10 cases of acute renal failure, and 10 cases of chronic renal failure from the final stage of chronic glomerulonephritis, malignant nephrosclerosis, diabetic nephropathy, and cortical necrosis. The following were common evidences for chronic renal failure: much reduction and wide deficiencies of filling in the cortex, increased filling of vasa recta, narrowing and spiralling of interlobular arteries and cortical afferent arterioles, appearance of giant glomeruli, rarefaction of the peritubular capillary plexus, and relative preservation of glomeruli in the juxtamedullary zone and vasa recta in the medulla may be the major pathway, after the interlobular arteries and afferent arterioles in the subcapsular cortex are destroyed, and these vascular architectural changes may be intimately related to the pathophysiology of chronic renal failure.