Abstract In normal rabbits, under Nembutal anesthesia, the total protein and albumin content of the arterial blood serum are significantly higher than the same fractions of the renal venous blood serum. This condition is reversed in the rabbits after removal of more than 15 ml. blood/kg. Renal innervation plays a role in the regulation of the protein concentration in the renal venous blood, after hemorrhage. No significant difference of protein fractions in the arterial and renal venous blood sera has been observed in a series of rabbits with experimental renal hypertension. Parallel estimations of color intensity of previously injected Evans Blue, and of the protein fractions (by electrophoretic and turbidimetric methods) in the arterial and renal venous blood specimens of normal rabbits corroborate the possibility of a renal mechanism of albumin storage.