Des-gamma-carboxyprothrombin (DCP) is an abnormal prothrombin with a decreased number of gamma-carboxylated glutamic acid residues in the Gla domain. DCP is also known to be an effective serological tumor marker for hepatocellular carcinoma (HCC), and highly sensitive methods of detecting serum DCP have enabled the detection of early and smallsized HCC in clinical settings. Several immunohistochemical studies have suggested that excessive production of DCP in HCC tissues may relate to worse tumor behavior such as the presence of vascular invasion and intrahepatic metastasis of HCC cells. Clinical availability of DCP, therefore, might be a more significant factor in the diagnosis of tumor behavior in HCC patients. Recently, some studies have suggested that DCP may play an important role in cancer progression via induction of cancer cell proliferation and angiogenesis around HCC tissues. Thus, DCP is expected to be effectively used not only as a tumor marker but also as a target of drug discovery.