The injection of neoprene into the renal vessels in vino causes vasoconstriction which interferes with the complete filling of the vascular system of the kidney. This vasoconstriction can be prevented by the production of ischemic vasodilatation prior to the use of the injn. mass. Satisfactory neoprene casts of the renal vascular bed were obtained by the use of this technic, but the casts do not provide reliable information regarding the intrarenal distr. of the circulating blood. The only consistently existing vessels which directly communicate between the renal artery and vein without an intervening glomerulus are situated in the hilum of the kidney. These vessels are not true arteriovenous shunts but probably are part of the vascular bed of the hilar and pelvic tissues of the kidney.