An autopsy case of carcinosarcoma of the liver in an 84-year-old man is described. The 14 x 6-cm solid tumor was located in the hilus to the left lobe and was grayish-white with some translucent areas. Histologically, the tumor consisted of an intimate mixture of adenocarcinomatous and chondrosarcomatous elements with transitional areas in between. Immunohistochemically, cells of the adenocarcinomatous elements were positive for cytokeratin but negative for S100 protein, whereas cells of the chondrosarcomatous elements showed the reverse staining pattern. Cells of transitional areas were positive for both cytokeratin and S100 protein. Most previously reported cases of carcinosarcoma of the liver have involved elderly men and have had a poor prognosis. The findings of the present case support the view that carcinosarcomas represent carcinomas that develop a sarcomatous element via metaplasia of the epithelial element.