For 15 to 20 years, electron microscopy studies have shown that some hereditary renal diseases are characterized by various abnormalities of the basement membranes. In the nail-patella syndrome, in Alport's syndrome and variants, and in benign familial hematuria, the changes involve the glomerular basement membrane (GBM). In nephronophthisis, the tubular basement membrane (TBM) is affected. These histopathologic features are not uniform. The progress afforded by biochemistry, immunology, and molecular biology allows us to compare these various lesions, to analyze their biochemical characteristics and their antigenicity, and to hypothesize as to the mechanisms involved.