The qualitative and quantitative morphological evaluation of the juxtaglomerular apparatus (JGA) is given on the basis of electron microscopic examinations of JGA in renal biopsies of the patients with mesangio-proliferative and mesangiocapillary glomerulonephritis with or without hypertension. An increase in the total number of JGA cells including granular ones is observed in chronic glomerulonephritis. In hypertensive forms of glomerulonephritis, particularly those with high proteinuria, rhomboidal protogranules were prevalent in the cytoplasm of epithelioid cells, in glomerulonephritis without hypertension and marked proteinuria spheric and lipofuscin-like granules were predominant. In glomerulonephritis with hypertension, an analysis of granule formation in JGA epithelioid cells by formparameter revealed a significant predominance of elongated granules (rhomboidal protogranules), and a lineal correlation analysis demonstrated a strong association between the degree of JGA activation assessed by formparameter values and the duration of the disease. An increase in the number of granulated cells in JGA correlated with the increased activities of glomerular mesangial cells and the appearance of epithelioid cells in the afferent arteriolar wall. The dystrophic changes of adrenergic nerves and their endings developing in glomerulonephritis may be a manifestation of overcharge of nervous apparatuses, particularly in the presence of arterial hypertension.