PURPOSE: CD44 is a multifunctional adhesion molecule in cell-to-cell and cell-to-matrix interactions. This transmembrane glycoprotein exists in either standard or variant form, with the variation originating in alternative splicing. This study was designed to evaluate the role of CD44v6, one of the CD44 isoforms, in hepatocellular carcinoma and cholangiocarcinoma. MATERIALS AND METGODS: Immunohistochemical expression of CD44v6 was studied in 7 normal livers, 14 hepatocellular carcinomas and 16 cholangiocarcinomas, that were formalin fixed and paraffin embedded. RESULTS: CD44v6 was frequently expressed in the normal hepatocytes and hepatocellular carcinomas. Expression was not noted in the normal bile duct within the portal tract. CD44v6 was positively expressed in some of the proliferating bile ducts (43%) and cholangiocarcinomas (69%). CONCLUSION: CD44v6 expression may be more important in the stepwise carcinogenesis of the bile duct than in the normal hepatocyte, but further study is needed.