Morphologic changes of extracapillary and chronic progressive glomerulonephritis with contracted kidneys, resembling those of adult human chronic glomerulonephritis, were induced in rats by a single injection of the purified glycopeptide and Freund’s incomplete adjuvant into the hind footpads. The purified glycopeptide was prepared by TCA treatment or DEAE-cellulose chromatography from the nephritogenic glycopeptide which is known to have the ability to induce typical morphologic changes of membranous glomerulonephritis. As demonstrated in this report, the purification procedures result in complete elimination of contaminating free amino acids from the nephritogenic glycopeptide. The basic pathogenesis of the new experimental model of proliferative glomerulonephritis (including typical chronic glomerulonephritis) appears to have other than immune complex mechanisms.