Necrotizing enterocolitis is a serious abdominal disease in infants during the first 2 months of life. The earliest radiographic finding on frontal abdominal films is initially distension of the small bower, secondly of the colon, and pneumatosis intestinalis. Pneumatosis intestinalis is not pathognomonic for necrotizing enterocolitis; it can occur throughout life in different abdominal diseases. It can be a serious prognostic sign for abdominal ileus, but it may also occur in non-critically ill patients. Radiographic diagnosis in childhood is achieved with a frontal film of the abdomen in the prone position, and to detect a possible perforation, a left lateral abdominal decubitus exposure is necessary. Sonography and duplex sonography are helpful in evaluating progressive changes, the clinical course and the differential diagnosis.