To assess the renal effects of hemoglobulin infusion, intrarenal hemodynamics were studied in 14 dogs using radioactive microspheres following the infusion of hemoglobin and stroma. Fractional renal microsphere distribution in the outer cortex remained at control levels following the infusion of hemoglobin. When the infusion of stroma followed, there was a 4.3 per cent, p less than 0.01, increase in the outer cortex microsphere distribution at the expense of the inner cortex, p less than 0.05. When the order was reversed, the stroma suspension being infused first, again there was a significant increase in the outer cortex distribution--6.1 per cent; p less than 0.01. When the infusion of hemoglobin followed, the outer cortex microsphere trapping reverted to control levels. These data revealed no effect upon intrarenal blood flow following the infusion of hemoglobin. The previously reported renal toxicity of hemoglobin infusion is, therefore, probably secondary to contamination with stroma. Hemoglobin should be further investigated for use as an ideal resuscitation fluid.