Four cases of fulminant hepatic disease caused by lymphoreticular infiltration are described. All 4 patients died within a few weeks and clinical diagnoses included viral hepatitis, alcoholic hepatitis, and drug hepatitis. A diagnosis of malignancy was made prior to autopsy in only 1 of the 4 patients. Autopsies revealed typical malignant histiocytosis in 3 patients and the fourth had a primitive lymphoreticular malignancy with malignant histiocytosis the favored diagnosis. The extent of the liver infiltrate as judged histologically was mild compared with the severe clinical illness. Randomly scattered foci of necrosis associated with the malignant infiltrate were seen in the 2 patients who had marked elevations of serum glutamic oxaloacetic transaminase.