AbstractA quantitative study of glomerular basement membrane (GBM) changes in 16 cases of IgA nephropathy was carried out on two whole glomeruli per case using a wide‐field electron microscope. We found that GBM changes are observed more frequently than previously reported, although some changes are small and uneven in distribution. Changes include (a) attenuation, (b) lytic attenuation, (c) garland‐shaped widening of the GBM, (d) dome‐shaped widening of the GBM, and (e) disruption of the GBM. There was some correlation between the severity of light microscopic findings and the percentage of GBM affected by complicated changes ((b)–(e)). The percentage of complicated GBM changes correlated with the amount of proteinuria at biopsy. The frequent occurrence of GBM changes in IgA nephropathy suggests that they might be playing a role in the pathogenesis of IgA neph