Urinary tract infection is a common and frequently recurring condition in children. The susceptibility of the host, the presence of urinary tract abnormalities, and the virulence of the urinary pathogens are of primary importance in the development of the infection. Renal parenchymal scarring, hypertension, and renal insufficiency are well-established complications of the infection in children. To reduce the risk of renal damage, diagnosis and treatment must be prompt. The diagnosis demands radiologic evaluation of the urinary tract in all boys, all children younger than 5 years, all patients with voiding dysfunction, and school-aged girls with recurrent infection to identify those patients with vesicoureteral reflux, obstruction, or other urinary tract abnormalities. Both voiding cystourethrography and renal ultrasonography are the initial examinations to use to determine the next appropriate study. Children with vesicoureteral reflux or with recurrent urinary tract infections should receive prophylactic antibiotic therapy and should be observed closely to prevent renal scarring.