Cellular transplantation represents an alternative to liver transplantation for the treatment of end-stage liver disease and liver-based inborn errors of metabolism. In order for cellular transplantation to be successful, an optimal source of cells for transplantation needs to be identified and the molecular mechanisms regulating their engraftment, proliferation, and functional differentiation elucidated. Here we describe a detailed protocol for the isolation, selection, and transplantation into an injured adult rat liver of a defined population of late gestation fetal rat hepatocytes. Also described is the methodology for assessing the purity of the selected cells and the efficiency with which they repopulate the adult liver. Our approach provides an in vivo model to study the molecular pathways involved in liver repopulation.