Thirty-eight kidneys from 20 children were studied with diuretic renography and the findings in 32 kidneys were compared with the results obtained using IVP. The diuretic renography findings were consistent with those of the IVP in 72 percent of the patients. The main disparity was the dilated nonobstructed pattern observed in the kidneys with normal IVP's, which is pointed out as being an asset of diuretic renography in revealing the functional status of kidneys. The sensitivity in detecting true obstruction was found to be 67 percent (4/6), and the specificity 95 percent (20/21). The accuracy of the technique was 85 percent with a false (+) rate of 5 percent (1/21) and false (-) rate of 33 percent (2/6). Diuretic renography is a simple, safe, non-invasive technique, easily applied to children with high specificity in excluding obstruction in a dilated renal pelvis.