A minimal change nephrosis was induced in rats by a single intraperitoneal injection of puromycin aminonucleoside (100 mg/kg). This resulted in increased urine protein output, plasma creatinine, blood urine nitrogen, and relative kidney weight. Electronoptically, there was a retraction of the glomerular podocytic foot processes. When human α<sub>1</sub>-acid glycoprotein was injected at 600 mg/kg intravenously on experimental days 6, 7, 8, and 9 into these animals, urine protein output decreased significantly, and the number of podocytic foot processes increased significantly. α<sub>1</sub>-Acid glycoprotein is rich in sialic acid and largely negatively charged. Its therapeutic role in nephrosis, which is characterized by a loss of sialic acid and a loss of negative charge, thereby leading to a loss of permselectivity, is discussed.