Simultaneous tagged red cell and tagged plasma albumin concentration-time curves were obtained from the renal vein without recirculation, following rapid injection of the indicators into a renal artery. The mean transit time of the red cells was consistently faster than that of the plasma albumin, but the washout downslopes of the indicators was found to be identical. This is interpreted as indicating that some red cells are shunted through those pathways of shortest length. The dynamic circulating hematocrit of the kidneys averaged 89 per cent of the large vessel hemato-crit. Intrarenal circulating blood volume averaged 24 ml./100 Gm. of dog kidney