In potential living kidney donors, glomerular filtration rate (GFR) is often evaluated from the creatinine clearance (Ccr) or is predicted using formulas based on serum creatinine (SCr) or cystatin C (SCys) concentration. Ultrasonography is used to evaluate renal structure and dimensions. The objective of the present study was to evaluate the possibility of estimation of GFR from echographic renal dimensions in 66 potential live kidney donors (46 women and 20 men; age range, 25-73 years). The GFR was measured as the renal clearance of technetium 99m diethylenetriamine pentaacetic acid. The GFR was also estimated from the SCr concentration using the Cockcroft-Gault (CG-Ccr) and Modification of Diet in Renal Disease (MDRD-GFR) formulas and from SCys (Cys-GFR). Renal diameters were measured using conventional gray-scale renal ultrasound to estimate total and parenchymal renal volume using ellipsoid formulas. The GFR was predicted from renal dimensions on the basis of their relationship to measured GFR. Estimates of GFR obtained using renal volume more close correlated with measured GFR than did CG-Ccr, MDRD-GFR, or Cys-GFR. The mean difference from measured GFR was null. The GFR estimated from renal volume demonstrated better agreement with measured GFR and a lower prediction error vs values from the other prediction formulas (18.3 vs 22-34 mL/min). The GFR values predicted from renal volume were quite accurate as indicators of GFR less than 80 mL/min. In potential living kidney donors, sonographic renal volume provided more accurate estimates of GFR, with lower prediction error, compared with formulas based on SCr or SCys.