A b stra c t. We carried out a retrospective investigation in 220 patients to assess the influence of various parameters on the long-term course of membranoproliferative glomerulonephritis (MPGN) type 1.50 patients (23%) died during the follow-up period of 59 months on average, in another 57 (26%) end-stage renal failure developed. 54 patients (24%) suffered from chronic renal failure, stable renal function (creatinine below 1.3 mg/dl) was preserved in 59 patients (27%).5 years after biopsy 49% of the patients had already died or needed regular dialysis treatment; after 10 years this proportion increased to 64%. Morphological findings: The outcome was with the exception of focal crescent formations -not determined by the severity of glomerular changes ; the survival rate, however, decreased significantly, if tubulointerstitial lesions were present as defined by acute renal failure, interstitial fibrosis ora combination of both. Clinical parameters; A progressive deterioration of renal function and an increasing number of renal deaths was noticed, when elevated serum creatinine levels at the time of biopsy and high blood pressure values during the follow-up period were observed. 26 patients died from hypertension, 18 of whom before reaching end-stage renal failure. Nephrotic syndrome and the degree of proteinuria as well as antiphlogistic and immunosuppressive treatment did not influence the prognosis of MPGN type 1.Studies on the long-term course of membranoprolifer ative glomerulonephritis (MPGN) have previously been carried out only on small numbers of cases, due to the rarity of the disease [1 13]. The prognosis is generally considered unfavorable [1-16], but there is still uncer tainty about the factors causing the progression to endstage renal failure or even death of the patient. In earlier investigations [14,[17][18][19] we noticed certain correlations between the severity of tubulointerstitial changes at the time of biopsy and renal function in MPGN. Therefore we were interested in determining whether, and to what extent, these changes as well as the clinical parameters blood pressure (BP), creatinine, proteinuria and hematu ria are of prognostic significance.1 Supported by the Deutsche Forschungsgemeinschaft (DFG). Material and MethodsAmong 36000 patients in our renal biopsy registry we found 346 in whom idiopathic MPGN was diagnosed between 1965 and 1984. By further investigations (immunohistology, electron microscopy) 108 patients had to be excluded from our study because primary diagnosis was not correct. They either suffered from other renal disorders (endocapillary/mesangioproliferative/membranous glo merulonephritis) or renal involvement due to underlying diseases such as lupus erythematodes, cryoglobulinemia and monoclonal gammopathy/multiple myeloma: 18 patients with MPGN type II (dense deposits) were also excluded. In the remaining 220 cases (male:female ratio = 1.75:l: mean age 36.4± 15.5 years) the lightmicroscopic diagnosis of MPGN was confirmed and type I (subendothelial deposits) could be ...