Biopsied renal tissues from patients with IgA nephropathy (IgAN; 28 cases) and with non-IgA mesangial proliferative glomerulonephritis (PGN;12 cases), and normal renal tissues obtained from kidneys removed for malignancies (11 cases) were included in this experiment. iNOS message was present in about 73% tissues from IgAN and PGN patients, which was supported by histochemical findings and the iNOS positive cells were predominantly in the tubulointerstitial areas where infiltration of monocytes/macrophages was abundant.