Recent studies has proved that high proportion of reflux episodes in Gastro Esophageal Reflux Disease(GERD) were non acidic ,and could not be detected by classic pH metry alone, especially less than 2 years, in whom nutrition is mainly depending on milk .It was too necessarily to improve a new technique (Multichannel Intraluminal Impedance MII) ,and by this any retrograde flow to the esophagus can be detected . The aim of this study was to determine whether pH-monitoring alone is sufficient to diagnose the Gastro Esophageal Reflux Disease (GERD),and how much the diagnosis was improved after Multichannel Intraluminal Impedance (MII) has been added to the standard pH catheter in children less than 2 years.