The prenatal ultrasound detection of urinary tract malformations presents opportunities for fetal intervention and formal screening programmes. As yet, the benefits of intervention and screening are largely unproved. The natural history of many prenatally detected uropathies in asymptomatic infants is not known. Enthusiasm for early postnatal surgical intervention in these infants may be misplaced. Information on the fetal urinary tract derived from ultrasound should be applied selectively.