It is hypothesised that chronic progressive kidney disease may be mediated by abnormalities of lipid metabolism. A series of self-perpetuating secondary events follows an initial glomerular injury. Increased glomerular basement membrane permeability leads to loss of lipoprotein lipase activators, resulting in hyperlipidaemia. Circulating low-density lipoprotein binds with glycosaminoglycans in the glomerular basement membrane and increases its permeability. Filtered lipoprotein accumulates in mesangial cells and stimulates them to proliferate and produce excess basement membrane material. The proximal tubular cells metabolise some of the filtered lipoprotein and the remainder are altered on passage down the nephron. Luminal apoprotein precipitates, initiating or aggravating tubulo-interstitial disease, if the intraluminal pH is close to the isoelectric point of the apoprotein. The hypothesis offers new approaches to the study of chronic progressive kidney disease by proposing a major pathogenetic role for lipid abnormalities.