Liver biopsy specimens with or without liver diseases were examined immunohistochemically to determine the distribution of endothelial cell markers, factor VIII-related antigen (FVIII-RAg). Ulex europaeus agglutinin I (UEA-I) lectin and PAL-E. We also investigated the localization of laminin, a component of the basement membrane. In normal livers, FVIII-RAg, UEA-I and laminin were negative in sinusoidal endothelial cells, but positive in blood vascular endothelia of the portal area. The antigen detected by PAL-E was distributed in venous endothelial cells. PAL-E did not label endothelial cells of the artery. In the lobule, immunoreactivity with PAL-E was weakly detected only in some sinusoids of the periportal area. In chronic active hepatitis and liver cirrhosis, FVIII-RAg and UEA-I stained endothelial cells of neovasculatures in the enlarged portal areas of the fibrous septum surrounding pseudolobules. Some sinusoidal endothelial cells in cirrhotic livers were reactive to UEA-I and FVIII-RAg, whereas PAL-E-positive cells were found rarely in the pseudolobules. In carcinomatous sinusoidal endothelial cells, FVIII-RAg, UEA-I and PAL-E were strongly stained. Laminin underlay these carcinomatous sinusoids. These suggest capillarization of sinusoids in hepatocellular carcinoma. The histochemical approach using endothelial cell markers could be a practical tool in the diagnosis of hepatocellular carcinoma.