Five patients of the pediatric age group are reported in whom defects in the liver scans appeared and persisted following abdominal irradiation for malignant disease. At least a part of the liver in each case had been included in the treatment fields. The single dose equivalent in each case was in the range of 1,400 r, and the 6 week equivalent dose, 4,250 r. In all cases, a sample of the area of liver affected was examined histologically and demonstrated the primary lesion to be hepatic venous obstruction at the sublobular level. The liven scanning and histopathologic changes reported are further evidence that the liver is a more radiosensitive organ than previously believed.