Three sibling and two isolated-case perinates (4 newborn, 1 stillborn) died with siderotic cirrhosis and widespread parenchymal siderosis, the latter similar to that seen in both hereditary and secondary hemochromatosis. Reticuloendothelial siderosis was absent, as occurs in primary hemochromatosis. Studies of iron metabolism were performed antemortem in two of the siblings and ante-, post- and internatally in their mother, who showed hyperferremia antenatally. The only finding in the affected family suggestive of hereditary hemochromatosis was the commonly associated HLA haplotype (A3, B7) in the mother and an infant. Liver morphology, including immunocytochemistry and ultrastructure, was similar in the 5 infants and suggested that liver disease commenced as massive necrosis in midfetal life. Histologic grading and chemical assays for iron and copper on liver and spleen of the 5 index cases were compared with 26 controls; placentas were compared with 12 control placentas. Hepatic iron concentration, but not hepatic copper concentration, was significantly increased in index cases, compared with controls. Hepatic iron to copper ratio was significantly increased in index cases, compared with controls, but this ratio was unaltered in spleen and placenta. Total hepatic iron, but not total hepatic copper, was significantly increased in index cases, compared with a subgroup of 11 controls of low gestational age, similar to the fetal stage when liver disease commenced in utero. The results suggest that, irrespective of the fetal liver disease being genetic or acquired, hepatic iron overload was directly involved in pathogenesis.