The hepatocyte is the smallest functional entity of the liver and executes the majority of this organ's -metabolic functions. Hence, hepatocyte transplantation has become a versatile alternative to whole organ liver transplantation. This novel treatment option is based on the assumption that transplanted -hepatocytes integrate into the host liver, proliferate at the site of tissue damage, take over the long-term hepatic -synthetic capacity, and thus substitute for the diseased host tissue. However, clinical success is still waiting for a breakthrough, likely because of two major reasons including (1) the scarcity of cadaveric donor livers and (2) the largely poor quality of cells isolated from marginal quality donor organs. Therefore, alternative cell sources have to be established to further prompt the clinical success of hepatocyte transplantation. Due to their multiple differentiation potential and nearly unlimited availability, stem cells are an attractive -alternate resource. Because of both clinical and ethical objections, adult stem cells are often preferred over embryonic stem cells as a starting material. Recent studies have demonstrated the ability of mesenchymal stem cells derived from various tissues to differentiate into hepatocyte-like cells in vitro as well as showing specific hepatocyte functions in vivo after transplantation into the livers of mice or rats.