In this article, emphasis is placed on those conditions that appear as the idiopathic nephrotic syndrome but that are more likely to result in progressive renal failure. Four conditions, membranoproliferative glomerulonephritis (mesangiocapillary glomerulonephritis), mesangial proliferative glomerulonephritis, membranous nephropathy, and focal segmental glomerulocosclerosis, account for 12 to 15 per cent of cases of idiopathic nephrotic syndrome during childhood. The further aim of this article is to focus on recent progress in our understanding of these conditions and to remind readers that little is known regarding the etiology and pathogenesis of each, and that effective, clearly proven forms of treatment for each are not apparent currently.