The intrarenal hemodynamics of nine dogs were studied using 15 micron diameter plastic radioactive microspheres labeled with either 85Sr or 141Ce injected before and with the alternative isotope injected 30 minutes after the induction of sepsis. Total renal microsphere trapping increased by 30.6 per cent, p less than 0.01, after the induction of sepsis. The glomerular filtration rate was unchanged. Microsphere trapping in the outer and inner cortex increased by 36.9 per cent, p less than 0.005, and by 20.3 per cent, p less than 0.05, respectively, reflecting increased renal blood flow. Fractional renal microsphere distribution in the outer cortex increased from 70.0 to 73.4 per cent, p less than 0.01, following the induction of sepsis. These data confirm that sepsis results in renal vasodilatation. In addition, a shift in intrarenal blood flow to the outer cortex was demonstrated. Since the outer cortex is perfused with blood which first passes through the inner cortex, it can be hypothesized that renal blood flow in septic states may be passing through dilated glomerular vessels unable to trap microspheres in the inner cortex or passing through precapillary open arteriovenous shunts, or both, thereby bypassing inner cortical functioning glomeruli. This may partly explain the decreased renal function associated with increased renal blood flow in septic states.