To investigate whether radiographic findings could be used to predict pan-necrosis (necrosis of 75% or more of the jejunum, ileum, and colon), we reviewed the serial abdominal radiographs and clinical records of 147 infants with necrotizing enterocolitis. Pan-necrosis occurred in 29 infants (20%) and was always fatal. The presence and degree of pneumatosis intestinalis, pneumoperitoneum and portal venous gas were studied. Pan-necrosis occurred least frequently in infants with mild or moderate pneumatosis intestinalis (8% and 12%, respectively), and with moderate frequency in those with pneumoperitoneum (33%). Pan-necrosis was found most frequently in infants with severe pneumatosis intestinalis (56%), portal venous gas (61%), or the combination of severe pneumatosis intestinalis and portal venous gas (79%). The mortality rates in these three groups were 63%, 65%, and 86%, respectively. Thus, infants with the worst outcome (those who develop pan-necrosis) can be identified on plain films by detection of severe pneumatosis intestinalis and portal venous gas.