To evaluate cystourethrography in the era of fetal screening, we evaluated retrospectively the clinical and imaging findings of all children up to the age of 1 year who underwent a cystourethrogram in a 5-year period (1987-1992). There were 292 children, 64 neonates (<1 month, 51 boys, 13 girls) and 228 infants (1 month-1 year, 111 boys, 117 girls). Hydronephrosis detected prenatally and confirmed after birth by US was the indication for cystourethrography in 88 children (72 boys, 16 girls). This 4.5 to 1, male to female ratio is very unusual compared to children with urinary tract infection, the great majority of whom are girls. The findings based on imaging studies in these 88 children with hydronephrosis included 31 with vesicoureteral reflux (VUR) (in 4 this was secondary), 23 with obstruction at the ureteropelvic junction (UPJ), 13 with multicystic dysplastic kidney, 2 with obstruction at the ureterovesical junction, 1 with ectopic ureterocele and 1 with posterior urethral valves, both the latter without reflux. Eleven children had normal postnatal studies and six children were lost to follow-up. Urinary tract infection (UTI) was the indication in 163 children (62 boys, 101 girls). Forty-one children were examined for other causes. Although most cases of hydronephrosis were detected on fetal screening, UTI was still the most common indication for cystourethrography and some significant abnormalities were found in these symptomatic children.