Screening for urinary tract infection was carried out in 23,427 schoolgirls, aged 5 to 14 years, using Uricult and, for hematuria, glycosuria and proteinuria using Hema-combistix. Cultures of 10(5) colonies per ml. or more on two occasions were obtained in 2.3% and a positive culture was confirmed by the family physician using standard culture techniques in 82.7% of cases, giving an overall incidence of infection of 1.9%. Fifty-eight percent of these children had no previous history of any urinary tract symptoms. Of the infected group 9.5% had pyelonephritic scarring, 58.7% chronic cystitis and 58.7% urethral stenosis. Two additional cases had unilateral ureteropelvic junction obstruction with hydronephrosis. Reflux occurred in 26.6% of those investigated by voiding cystogram. In 58% of cases the urinary tract infection was not accompanied by significant proteinuria, hematuria or pyuria.Proteinuria was detected on two occasions in 1.6% of the children and confirmed by the family physician in 33% of cases, giving an overall incidence of 0.5%. In this group 9.2% had evidence of pyelonephritic scarring without a positive urine culture.Hematuria was detected on two occasions in 0.6% of the children and was confirmed by the family physician in 53%, giving an overall incidence of 0.3%. Only one case with pyelonephritic scarring was seen in this group.Of the 25 cases with pyelonephritic changes only six had been previously diagnosed radiologically.Four previously unrecognized diabetics were also detected.