In this prospective study 101 sonographic examinations of superior mesenteric artery blood flow velocities, indices and blood flow volume were consecutively performed in 41 newborn to diagnose necrotising enterocolitis (NEC). Intramural and portal venous gas was also estimated. The artifacts of air in the AMS and the portal system were examined in an experimental study. The results of sonography and abdominal radiography were equivalent in the case of definitely established NEC, portal venous gas being more sensitive to detection by sonography. Abdominal radiography was indicated as the primary examination in case of a clearly identified clinical course. Sonography should be performed so that fewer radiographs will be required in the following course of disease.