Hematemesis is not infrequent occurences in the neonatal period. Physician's first task is to determine whether this blood is maternal in origin or whether the infant is bleeding internally. Fetal blood indicates one of a variety of lesions and its source may be difficult to determine. The causes are esophagitis, peptic ulcer of the stomach or duodernum, hemorrhagic disease and pulmonary hemorrhage etc. We have experienced a case of massive hematemesis that occured in a 1 day of life. we conducted 24 hour pH monitoring, upper gastrointestinal barium series, and endoscopy with biopsy. this case showed esophagitis due to gastroesohageal reflux and errosive gastritis by above procedures. If there is hematemesis during the neonatal period, the esophagitis and gastritis should be considered.