The effects of slow and relatively rapid infusions of modified human globin were studied in 6 human subjects (normals). Following control studies in which urine flow, clearance of PAH, [p-aminohippuric acid],Na excretion, R.B.C. [erythrocyte] agglutinability, sedimentation rate, and hematocrit were done, the patients received varying amounts of modified human globin, at different rates of infusion. In none of the patients was there any striking change in R.B.C. agglutinability, sedimentation rate, or hematocrit. Likewise, no striking increases in urine flow or PAH clearances were noted. There was a slight increase in the rate of Na excretion with globin as compared to the controls. These data are in marked contrast to the renal hemodynamic effects of hemoglobin from which modified human globin is derived. A possible explanation for the differences is offered. In essence this explanation concerns the absence of the Fe of hemoglobin which is available for the production of ferritin by the kidney. Ferritin is known to be antidiuretic. The globin used contains only traces of iron.