Abstract: Objective To study the homing capacity of allograft mesenchymal stem cells (MSCs) transfected with a green fluorescent protein (GFP) retroviral construct to the liver of rats. Methods MSCs were obtained from rat bone marrow and cultured in vitro in conditional DMEM medium supplemented with 10% fetal bovine serum. The MSCs were identified by the monoclonal antibodies of CD29, CD44, CD34, CD45, CD90, SH-2 and SH-3 followed by transfection with a GFP retroviral vector. After ex vivo expansion, the transfected MSCs were infused through the tail vein or portal veins of rats, some of which were subjected to treatment with carbon tetrachloride (CCl₄) to induce centrolobular liver necrosis. On days 3 and 7 after transplantation, the liver was removed from each recipient and evaluated for the presence of GFP transgene in purified genomic DNA using sensitive real-time PCR. Results All the rats receiving GFP-labeled MSCs survived until the study had been completed. GFP transgene in purified genomic DNA were detected in the livers of all the rats with GFP-labeled MSC infusion by sensitive real-time PCR. DNA copy numbers of GFP in the liver were higher in rats with CCl₄ treatment than in those without the treatment. Infusion of the MSCs through the tail vein or the portal vein did not produce significant difference in the mean DNA copy number in the liver of CCl₄-treated rats. In rats without CCl₄ treatment, the sites of MSC infusion, e.g. through the tail vein or the portal vein, produced significant difference in MSC homing to the liver, which was also related to the passage of time after MSC infusion. Conclusion In rats with liver injuries induced CCl₄, the timing and number of MSCs homing to the liver might be closely related to the presence of liver injury, but not to the site of MSC infusion, e.g. through the tail vein or the portal vein. MSCs possess homing capacity to the liver in normal recipient rats, and number of homed MSCs is related to the site of infusion and post-transplantation time.