Proteinuria and microhaematuria were observed in three siblings and one first-degree cousin. Histological examination of three kidney biopsies and one autopsy specimen shows the same diffuse glomerular lesions in all patients, characterized by mainly subendothelial but frequently transmembranous and mesangial deposits of a unique fibrillar structure, visible by electron microscopy. Examination by immunfluorescence gave inconstant findings. No serological abnormalities could be established. To our knowledge, such a pecular form of familial glomerulopathy has not been described so far.