• Screening children for asymptomatic bacteriuria to prevent pyelonephritis and renal scarring is widely recommended, but its cost-effectiveness has not been established. We reviewed published studies to determine the costs and benefits of screening toilet-trained, asymptomatic children for bacteriuria. Given the sensitivity and specificity of current screening methods (approximately 80% each) and the prevalence of bacteriuria in asymptomatic children (approximately 1% in girls and 0.03% in boys), screening 100 000 children would result in 19 897 (20%) false-positive tests; initial screening and two urine cultures to confirm the diagnosis of asymptomatic bacteriuria would miss 28% of 515 children with true bacteriuria, and cost nearly $2.9 million. There is no evidence that detection and treatment of children with asymptomatic bacteriuria prevents subsequent pyelonephritis or renal scarring. Screening for bacteriuria in asymptomatic children is costly, fails to prevent pyelonephritis or renal scarring, and should be discontinued as a part of routine well-child care.