Injection of a 50% glycerol solution intramuscularly into rats consistently caused azotemia associated with hemolysis, hemoglobinuria, and decreased urine osmolality. Survivors reinjected on days 7 and 35 demonstrated resistance to reinjection during both the azotemic and non-azotemic phases of recovery. Stable azotemic partially nephrectomized rats were injected to evaluate the protection afforded by a solute diuresis per nephron. The degree of hemolysis, as assessed by acute changes in hematocrit, was as great on reinjection as that seen initially. It is concluded that the azotemic renal failure induced by a previous injection of glycerol affords protection of renal function against subsequent glycerol injection while the solute diuresis in nephrectomized rats results in a lesser protection.