Immunohistochemical examination of puncture biopsies of the kidneys taken from 172 patients with mesangioproliferative glomerulonephritis (MPGN) showed its heterogeneity. MPGN with IgA deposits, MPGN with IgG deposits, MPGN with IgM deposits, MPGN with C3 deposits and immunonegative MPGN are separated. Clinically, nephrotic syndrome prevails in IgG and IgM, MPGN, various clinical forms occur in MPGN with C3 and immunonegative variants, hematuric and latent forms occur in MPGN with IgA. MPGN with IgM deposits has its own morphological and clinical features, this permitting to consider it as an independent form of glomerulonephritis.