The availability of US (ultrasonography) contrast media in the last few years has prompted investigation into their use in the diagnosis of vesicoureteral reflux (VUR) in children, a common cause of urinary tract infections (UTI) or pyelonephritis. We performed voiding cystourethrography (VCUG) and cystosonography (CSG) in the same session in 158 children (M/F 97/61, mean age 3.9 years, age range 0.1-12.7 years) with clinical suspicion of VUR, studied over a year with an ATL plus 3000 real-time scanner (ATL Ultrasound, Bothell, USA), equipped with 2- to 4- and 4- to 7-MHz convex transducers. US contrast medium Levovist (Schering, Berlin, Germany) was used. VCUG and CSG diagnosed 74 (24.2%) and 77 (25.2%) cases of VUR, respectively. There was no agreement in 67 cases (22%). The percentage of false negatives was similar and high with both techniques. CSG seems to be more sensitive in detecting intermediate (second- and third-degree) VUR. In spite of the moderate relative diagnostic adequacy of both methods, we believe that CSG is an alternative to VCUG, avoiding the risk of ionizing radiation, in the following conditions: (1) first diagnosis in females (not in males, due to the poor vesical and urethral anatomical detail it provides), (2) VUR follow-up, (3) VUR diagnosis in megaureters and/or in ureteroceles, and (4) VUR diagnosis in transplanted kidneys. Further improvements of CSG, both in US contrast media and in US technique, could possibly increase its sensitivity.