Membranoproliferative glomerulonephritis (CN) of types I and III was diagnosed in 154 patients (15.5% out of primary CN). Out of this number 60% were men. During biopsy, one third of the patients were normotensive, 40% were slightly hypertensive and one third suffered from severe hypertension. Mean proteinuria was 6.5 +/- 5.5 g/24 h. In two thirds of the patients erythrocyturia was higher than 35 mil. in Addis' sediment and the findings in the urine were characterised by the proportion between proteinuria and erythrocyturia (p less than 0.001). During biopsy in one half of the patients, the serum creatinine level was already elevated. The presence of creatininemia was found to be directly linked to blood pressure, proteinuria, the degrees of extracapillary proliferation, tubulointerstitial regression and vascular arteriolosclerosis. The cumulative duration of the kidney function within the period of 10-20 years was 41 or 28%, the cumulative cure amounted to 14% 10 years after biopsy.