Aims: Endothelin-1 (ET-1) contributes to renal fibrogenesis in several manners such as increasing collagen synthesis in mesangium, decreasing extracellular matrix (ECM) degradation by mesangial cells and stimulating mesangial contraction. The aim of our study was to investigate whether urine level of ET-1 (uET-1) could represent a useful biomarker of renal scarring and if so, to determine the optimal cut-off level for uET-1 to predict a renal scar. Methods: 44 children with renal scarring and 32 children without renal scarring were enrolled in the study. Urine ET-1 was measured by enzyme-linked immunosorbent assay. Results: Mean uET-1 level was significantly higher in the scar group than in controls (2.75 +/- 1.35 fmol/ ml vs. 0.68 +/- 0.41 fmol/ml, p = 0.001). The optimal cut-off level was 1.064 fmol/ml for uET-1 to predict renal scarring. Using this cut-off point, sensitivity and specificity were 97.73% and 93.91%, respectively. AUC was found 0.975 (95% CI 0.917 - 0.996) for uET-1. Mean urine Endothelin-1/Creatinine ratio (uET-1/Cr) was also significantly higher in the scar group than in the control group (4.04 +/- 2.29 fmol/mg Cr vs. 1.09 +/- 0.67 fmol/mg Cr, p = 0.0001). Using 1.67 fmol/mgCr as optimal cut-off level, sensitivity and specificity were 95.45% and 84.09%, respectively. AUC was 0.945 (95% CI 0.875 - 0.982) for uET-1/Cr. Conclusion: Our study suggests that both uET-1 and tiET-1/Cr can be used for prediction of renal scarring in children with normal renal function. Measuring urine level of ET-I can help us to avoid unnecessary DMSA studies if the patient's uET-1 level is found to be under the determined cut-off point.