PURPOSE: To evaluate the prevalence of abnormalities seen on sonography and renal scintigraphy, according tothe grade of vesicoureteral reflux (VUR) on in voiding cystourethrography (VCUG). MATERIALS AND METHODS: Onehundred and forty-nine patients (age range : 1 months - 10 years) with urinary tract infection underwentsonography, VCUG, and renal scans, and 32 showed VUR on VCUG. We retrospectively evaluated the frequency andcharacteristic findings of sonographic abnormalities according to the grade of VUR, and also the frequency ofcortical defects seen on renal scans of 32 patients with VUR. The remaining 117 patients without VUR were alsoevaluated for the frequency of abnormal findings seen on sonography and renal scans. RESULTS: Among 32 patients(49 kidneys) with VUR, abnormal findings were not detected in 17 (29 kidneys) on sonography ; thus, findings wereabnormal in 15(20 kidneys, 41%). Among these 20 kidneys, renal calyceal and/or pelvic dilatation and dilatation ofdistal ureter were seen in 11, all of which were grade 4-5 VUR. Renal pelvic dilatation only was noted in eightkidneys ; two were grade 1-3 and six were grade 4-5 VUR. Nineteen patients (24 kidneys, 49%) showed focal corticaldefects on renal scintigraphy. Six kidneys were grade 1-3, and 18 kidneys were grade 4-5 VUR. Of 117 patientswithout VUR, 34 patients (29%) showed renal pelvic dilatation on sonography and in 14 patients (12%), corticaldefects were seen on renal scintigraphy. CONCLUSION: Among 32 patients with VUR, 41% showed abnormal sonographicfindings and in 49%, cortical defects were seen on renal scintigraphy. With a higher grade of VUR, the prevalenceof abnormalities increased on both sonography and renal scintigraphy. Sonographic demonstration of renal calicealand/or pelvic dilatation associated with ipsilateral distal ureteric dilatation was the characteristic finding inhigh grade VUR.