Background: Gastroesophageal reflux disease (GERD) is one of the most common gastrointestinal pathology in infants and young children. Ultrasonography (US) has been considered to be a reliable diagnostic tool for GERD but the severity of GERD and the clinical implications based on imaging findings has not been evaluated. Aims: To compare the diagnostic value of lower esophageal US with that of barium swallow in demonstrating the severity of GERD. Materials and methods: Fifty one pediatric patients, age between 1 month to 12 years, 34 male and 17 female with clinical suspicion of GERD were included. The patients were initially submitted to barium swallow (BS) and subsequently to transabdominal US. During BS, the number of gastroesophageal reflux episodes was documented in a 5-minute period. Transabdominal US documented the number and duration of reflux episodes during a 5-minute period, the angle of His, mucosal thickness, and intraabdominal esophageal length (IAEL). Results: Duration and number of reflux episodes in US were significantly higher in patients that had severe gastroesophageal refluxes at BS. At US the cutoff point of 9.5 seconds (sensitivity 80%, specificity 60%) for reflux duration and more than 2 episodes in 5 minute ultrasound study (sensitivity 75%, specificity 58%) were defined to correlate with severe gastroesophageal reflux at BS.The angle of His, the esophageal wall mucosal thickness, and the IAEL did not correlate with the severity of GERD detected in BS. Conclusion: US can predict the severity of GERD. Therefore, except in the case of specific patients in whom mechanical causes are suspected to be responsible for GERD, BS can be replaced by US.