PURPOSE: To evaluate diagnostic usefulness of ultrasonography(US) in pediatric patient with urinary tract infection. MATERIALS AND METHODS: Fifty-five children with urinary tract infection underwent renal ultrasonography and voiding cystourethrography(VCUG). The imaging findings were analyzed retrospectively. RESULTS: Renal sonograms were normal in 34 of 55 children(62%). Five of 34 patients with normal sonogram had vesicoureteral reflux of grade I to III on VCUG. Renal sonograms were abnormal in 21 of 55 children(38%). Sonographic findings included hydronephrosis, hyperechoic kidney, nephromegaly, atrophic kidney, renal abscess, and duplex ureter. Eleven of 21 patient with abnormal SOhogram had vesicoureteral reflux of grade I to IV on VCUG. CONCLUSION: Ultrasonography is an useful and reliable initial screening examination in the investigation of children with UTI. Unfortunately US is neither sufficiently sensitive nor specific for detecting VUR. VCUG provides confirmative and valuable information about vesicoureteral reflux, and VCUG should be considered as a next modality for UTI. The combined use of sonography and VCUG provides more valuable information in urinary tract infection.