The quantity of urinary proteins and their molecular weight composition was analyzed in different experimental glomerulopathies using the SDS-PAA-electrophoresis. Masugi nephritis, heterologous and autologous immune complex nephritis as well as D-penicillamine induced glomerulonephritis were studied in rabbits, guinea pigs and rats. The procedure allows (1) to distinguish physiological from low grade glomerular proteinuria by their respective characteristic patterns in early disease stages (2) to follow up the disease course of individual animals without sacrifice and (3) to discriminate species specificity of physiological urinary proteins. It is recommended to use this technique of urinary protein analysis in experimental conditions, where mild glomerular damage is expected.