The correlation between urinary tract infection (UTI), vesicoureteric reflux (VUR) and renal scarring was studied in 89 patients (177 renal units; 1 solitary kidney) during the period 1997-2000. There were 63 males and 26 females; ages ranged from neonates to 14 years. UTI was diagnosed on the basis of a positive urine culture, VUR was diagnosed and graded by micturating cystourethrogram (MCU), and renal scarring was assessed by technetium 99 m Tc-dimercaptosuccinic acid (DMSA) scan. Ultrasonography (US) was done to evaluate renal tract dilatation and other structural abnormalities. A follow up DMSA scan was performed approximately 6 months after the initial scan. VUR was present in 106 of the 171 renal units in which it was studied and absent in 65 units. The majority of the VUR was grade V. Renal scars were seen in 90 of 177 renal units at presentation and in 72 of the 163 renal units studied at follow-up. Some information was lacking in 31 patients; hence, the correlation between UTI, VUR, and renal scarring was done in 58 patients. The majority of the suspected scars at presentation were not seen at follow-up, but most of the established scars persisted. Only 2 renal units showed scars for the first time on follow-up. On US, approximately 50% of normal kidneys showed either suspicious or established scars on DMSA scan, and patients with bilateral abnormality on US showed renal scars. Renal scars were seen in 15 of 23 children without VUR, 17 of 18 with unilateral VUR, and 16 of 17 with bilateral VUR. Thus, there is a cause-and-effect relationship between UTI and renal scarring that is made worse by VUR. DMSA scans have been shown to be the most reliable method of assessing renal scarring, and an abnormal US scan showing upper-tract dilatation or a structural abnormality may have a predictive value in the detection of renal scarring.