The purpose of the present study was to investigate whether human umbilical cord blood (UCB) as well as bone marrow (BM) can generate hepatocyte lineage cells in a simple culture condition. Mononuclear cells (MNCs) separated from UCB and BM were cultured in the presence of fibroblast growth factor (FGF)-1, FGF-2, stem cell factor (SCF), and hepatocyte growth factor (HGF). The cultured cells were analyzed for morphology and for the expression of mRNAs and/or proteins of hepatocyte lineage markers. Both the UCB and BM MNCs grown in the given culture condition yielded large, round cells that were adherent to the culture dishes. RT-PCR analysis showed that mRNAs of albumin (ALB), cytokeratin (CK)-18, and alpha-fetoprotein were expressed from day 7 in both the UCB- and BM-derived cells. Immunofluorescent staining showed that the large, round cells expressed not only ALB and CK-19 but also proliferating cell nuclear antigen, implying the proliferative potential of hepatocyte lineage cells. Therefore, UCB as well as BM can give rise to hepatocyte lineage cells in the simple culture condition with HGF, SCF, FGF-1, and FGF-2. These cells may be one of the potential candidates of cell sources for the cytotherapy of hepatic disease, although it remains to be determined if the hepatocyte lineage cells are derived from plastic hematopoietic stem cells or from liver stem cells that reside in UCB or BM.