The purpose of the present study was to perform an electron microscopic investigation of patients with chronic glomerulonephritis and to find correlations between the type of glomerular disorder and the features of the clinical course of the disease. 26 patients--16 female and 10 male aged 17-62 years (mean age, 34.5 years) were investigated. All patients were clinically diagnosed as having chronic glomerulonephritis with a disease duration ranging from 3 months to 2 years. The main clinical and laboratory parameters studied were presence of edemas, hypertension, proteinuria, hyperlipidemia, haematuria and renal failure confirmed by the creatinine clearance. A puncture renal biopsy was performed by classical methods under ultrasound guidance using a Vim-Silverman needle. An electron microscope Philips CM-12 was used in the study. We found in all patients a significant correlation between the degree of proteinuria and the marked deformation and edema of the podocyte pedicles. In making the integral histological diagnosis of chronic glomerulonephritis it is necessary to determine more precisely the mesangial involvement and the changes in the membrane by means of an electron microscopic study. This will be conducive to a reduction in the number of mistakes in diagnosing some primary chronic glomerulonephrites.