Chronic pyelonephritis is a disease of childhood that is carried on into adult life. Children under the age of 4 in whom UTI, vesicoureteric reflux and pyelotubular backflow coexist appear to be particularly at risk of developing kidney damage. Attempts to prevent kidney damage in adults by detection and treatment of covert UTI are doomed to failure because persistent bacteriuria in the adult is a consequence of underlying abnormality of the urinary tract rather than its cause. Our main hope for the prevention of kidney damage associated with bacteriuria and reflux is to detect and treat these conditions at the earliest possible age. The controlled trials of the value of treatment of bacteriuria and vesicoureteric reflux in childhood that are in progress in various centers in the United Kingdom should be allowed to continue and medical opinion as to the value of such treatments should not be allowed to crystallize before the results of these trials are known.