A characteristic pattern of hepatic parenchymal and portal venous abnormalities was seen with sonography in 12 infants with necrotizing enterocolitis (NEC). In five cases these changes were seen before any radiographic abnormalities were observed. Sonography of 232 infants without NEC did not show these changes. The sonographic abnormalities are believed to be caused by small amounts of gas within the portal venous system and hepatic parenchyma. Because of the simplicity of the sonographic examination and the sensitivity and specificity of the findings, abdominal sonography may be of great value in the early evaluation of infants suspected of having NEC.