112 cases of MPGN, whose diagnosis was made on light microscopy, were reviewed. Histological examination showed 66 cases of 'classical' MPGN, 33 of MPGN with a lobular pattern and 13 of MPGN with epithelial crescents. In 11 patients dense intramembranous deposits were observed. On immunofluorescence (95 cases) 62 patients showed deposits of C3 together with immunoglobulins, 20 had a predominant deposition of C3 and in 13 C3 alone was present. At the moment of biopsy 57 patients had nephrotic syndrome, 43 hypertension, 43 impaired renal function and 65 hypocomplementaemia. In 23 cases, one or more episodes of macroscopic haematuria occurred. The actuarial survival was 70% after 10 years and 50% after 20 years from onset. At last observation 25 patients were dead or on haemodialysis, 22 had impaired renal function, 62 had normal renal function and 2 were in complete remission. The histological variety with epithelial crescents had a significantly worse outcome. The presence of dense deposits or of any specific immunofluorescence pattern had no prognostic significance. Nephrotic syndrome, renal function impairment and hypertension indicated a poor prognosis: however, macroscopic hamaturia or hypocomplementaemia did not influence the outcome.