A case of cholesteryl ester storage disease (CESD) was found by liver biopsy in a 5-year-old boy. Hepatosplenomegaly, varying elevations of serum transaminases and hyperlipoproteinemia, type IIb, were detected clinically. The liver tissue was yellow. The cytoplasm of hepatocytes and Kupffer cells was foamy. In frozen sections these cells stained with dyes and histochemical methods for neutral lipids, unsaturated lipids, and cholesterol, but not with dyes for phospholipids and glycosaminoglycans. Under polarized light a large quantity of birefringent storage material was visible. We determined the lipid composition histochromatographically and found a very substantial increase in cholesteryl ester content and a moderate increase in triglycerides compared to control liver tissue. These findings are in agreement with our former case of CESD (1979). But in contrast to the liver tissue of the first patient there was more pronounced hepatic periportal and intralobular fibrosis in the second case. Remarkable amounts of ceroid storing histiocytes, so called "sea-blue histiocytes" were visible within the fibrous tissue. The granules of these cells stained with dyes for neutral lipids, phospholipids, glycosaminoglycans, and sea-blue with Giemsa in both frozen sections and paraffin-embedded liver tissue. They showed a yellow autofluorescence and were partly birefringent. Ceroid is believed to be the product of lipid peroxidation, binding to protein and polymerization. Therefore we suggest an additional deficiency of tissue antioxidants at the storage sites in such cases of CESD and this may potentiate liver fibrosis.