The microcirculation of hepatocellular carcinomas (HCCs) and surrounding tissue was observed three-dimensionally by scanning electron microscopy of vascular casts made from 10 livers at autopsy. The livers were perfusion-washed and cast with resin through both the hepatic artery and portal vein branches. The HCCs observed ranged from several millimeters to 3 cm in size. A vascular plexus proliferated around the HCC nodules in all cases. Both portal vein and hepatic artery branches proliferated markedly to form the plexus in 5 patients. These vessels communicated directly with the blood sinuses of the HCCs as feeder vessels. HCC cells replaced normal cells while maintaining the liver's trabecular structure in 2 cases. At the borders of these HCCs, there was direct communication between the hepatic sinusoids and the tumor blood sinuses. Efferent vessels of the tumors were generally difficult to identify but vessels resembling hepatic vein branches were detected in one 4-mm HCC nodule after microdissection. Thus, HCC was demonstrated to be supplied not only by the hepatic artery but also by the portal vein and hepatic sinusoids. This may be one of the reasons why cancer cells survive in the tumor margins and daughter nodules after transcatheter arterial embolization of HCC.