Primary mesangial proliferative glomerulonephritis without IgA deposition (non-IgA MsPGN) is one of the most common types of glomerular disease in China. In an attempt to investigate its clinical and pathological features, we reviewed 77 such cases from 380 patients with primary glomerulonephritis taken renal biopsies during 1980-1987. Prodromal upper respiratory tract infection occurred in 31 cases (40%). In immunofluorescence microscopy, prominent IgG granular deposits in mesangium were observed in 45 cases (58%). These features are quite different from those in western countries, indicating it might have different pathogenetic processes. According to the severity of mesangial lesions, the 77 cases were divided into 3 groups: mild (55 cases), moderate (14) and severe (8). In the patients with mild mesangial lesion and massive proteinuria, the therapeutic response to prednisone was similar to that in adult minimal change disease. In the moderate and severe groups, there was a significantly higher incidence of superimposed tubulo-interstitial lesions associated with hypertension, persistent renal insufficiency and a poor response to prednisone. This work showed non-IgA MsPGN covered about 20% of our primary glomerulopathy, which may be related to a higher incidence of infection. It was suggested that minimal change nephrotic syndrome, inspite of the variety of immunoglobulin mesangium deposits, could be treated as a single disease entity, and light microscopy is most important in offering prognostic information.