Abstract: In this paper. the effects of serum from 38 patients with IgA nephropathy on cultured gloumerular mesangial cells in vitro were studied. the IgA-CIC, IgG-CIC and IgM-CIC in the serum were measured by using ELISA. The results were summarized as follows: 1. the ~3H-TdR uptake into mesangial cells was markedly enhanced （P＜0.01） by the serum of IgA nephropathy on culture medium, and the increment was closely related to the severity of glomerular pathological changes (r=0.429; 2. the levels of IgA-CIC and IgG-CIC increased in the serum of patients with IgA nephropathy than those in normal controls （P＜0.05）; and 3. there was a close relationship between the amount of urinary protein and the degree of renal pathological changes （r=0.616）.