Gastroesophageal reflux (GER) is the most important disorder of the esophagus and the lower esophageal sphincter (LES) in early childhood. Functional disturbances with inadequate relaxation of the LES have to be considered as pathogenetic factors. In the 1st month many newborns have some disorder of motor coordination of the esophagus. After that time, persisting GER may be seen as a delay in maturation, which fades away by the end of the first half year. GER after 6-9 months is to be considered as a definitively pathological condition that will not spontaneously normalize. Nevertheless, it is important to realize that the typical clinical signs of reflux stop generally between the 6th and 12th month, and so simulate healing independent of whether spontaneous maturation occurs or there is continued existence of reflux. Reflux-induced apneic spells are severe complications of this esophageal disorder in the 1st year of life. Esophagitis, usually a late complication, occurs when the aggressive factors win their fight against clearance and mucosal resistance of the esophagus. Brachyesophagus and endobrachyesophagus are severe late complications.