The possible relationship between the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and renal scarring secondary to vesicoureteral reflux (VUR) has recently attracted attention and the DD genotype was postulated to be a risk factor for renal scarring. However, available data represent conflicting results. The aim of this study was to investigate the ACE gene I/D polymorphism and the other known risk factors for renal scarring in children with low- and high-grade VUR. The study included 96 (67 females, 29 males) patients (mean age at diagnosis 3.7+/-3.3 years) with VUR that were assessed for ACE I/D gene polymorphism. ACE genotypes were determined as II, ID, and DD using the polymerase chain reaction. The control group consisted of 103 healthy children with the same ethnicity to find the distribution of ACE gene I/D polymorphism in the population. The frequency of renal scarring was 80.8% in the high-grade reflux group and 34.3% in the low-grade reflux group. There was no difference between groups with renal scarring and without scarring with respect to gender, family history of VUR, age at diagnosis of VUR, associated urological abnormalities, frequency of urinary tract infection episodes, and the occurrence of bilateral or unilateral VUR. Genotype DD was found to be a significant risk factor for renal scarring in the study group by multivariate regression analysis (odds ratio 3.79, P=0.011). It was not a risk factor in high-grade reflux patients (odds ratio 0.60, P=0.62). However, it was a risk factor in low-grade patients with respect to renal scarring (odds ratio 4.0, P=0.024). Although renal scarring is not common in low-grade reflux patients, there may be scarring in some patients. DD polymorphism of the ACE gene is a significant risk factor in low-grade reflux patients with renal scarring.