The localization of PIVKA-II in liver tissue was studied by the immuno-staining method using monoclonal antibody. The cell lines derived from hepatoblastoma (huH-6), hepatocellular carcinoma (PLC/PFR/5), and normal liver (Chang) were used as materials for staining. We succeeded to stain PIVKA-II, when the materials were fixed in a formalin solution and frozen. In patients with hepatocellular carcinoma, PIVKA-II was stained in the cytoplasm of both hepatoma and non-hepatoma cells.