Reflux nephropathy is now a generally accepted term to describe small scarred kidneys discovered during childhood; it recognises the close association between this renal lesion and vesicoureteric reflux (VUR). This paper briefly reviews the pathogenic factors involved in reflux nephropathy and suggests that at least two main mechanisms operate: acquired segmental scarring due to intrarenal reflux and congenital maldevelopment (renal dysplasia). The spectrum of renal changes associated with VUR can be usefully divided on this basis and the opportunity to recognise by fetal ultrasound those renal lesions acquired in utero may further enhance our understanding of the congenital maldevelopment group.