Intrarenal haemodynamics were investigated in previously uninephrectomized dogs, immediately after release and on the third day following two hours clamping of the renal artery. Postischaemic renal failure (PIRF) was considered moderate or severe, if three days after clamping plasma NPN values were under or over 150 mg/dl, respectively. Renal blood flow (RBF) as determined by measuring the renal venous effluent and by radioactive microspheres did not differ significantly from controls either immediately after release, or three days following arterial occlusion. Glomerular filtration rate (GFR) was, however, severely depressed in all postischaemic kidneys. An increase in preglomerular and a decrease in postglomerular resistance was assumed, resulting in unaltered total vascular resistance and a sharp drop in glomerular capillary pressure. Radioactive microspheres revealed a shifting of intrarenal blood flow from the superficial cortex towards the deeper (juxtamedullary) cortical layers. Fractional flow to the outer cortex was decreased, that to the inner cortex increased, as compared with uninephrectomized controls.