A family group of first and second degree relatives is presented. Members of the group have vesico-ureteric reflux and/or duplex collecting systems. Renal scars of chronic pyelonephritis are seen. It is considered that because histological features are not always specific and because the relationship of renal scars to infection uncertain, chronic pyelonephritis is a diagnosis made on radiological evidence. It is suggested that the renal scars of this condition may result from vesico-ureteric reflux in infancy. Vesico-ureteric reflux is a congenital abnormality related to the position of the junction on the bladder wall. When double ureters are present, reflux is more common. The possibility that the congenital abnormalities are inherited, is discussed. The abnormalities in the family group presented, suggest that a single gene inheritance is possible, with variable expression and occasional lack of penetrance, and no sex linkage. This genetic basis of the abnormality, suggests that anatomical and physiological disturbances underly the development of renal scarring and are worth looking for more widely in the families of those already presenting with symptoms.