Background It is essential to establish an animal model for the elucidation of the biological behaviors of stemcellsin vivo.We constructed a chimeric animal model byin uterotransplantation for investigation of stem celltransplantation.Methods This chimerism was achieved by injecting the stem cells derived from the bone marrow of greenfluorescence protein (GFP)-transgenic mice into fetal mice at 13.5 days of gestation.Several methods such aspolymerase chain reaction (PCR), real-time PCR, fluorescence-assisted cell sorting (FACS) and fluorescencein situhybridization (FISH) were used for the observation of donor cells.Results Under a fluorescence microscope, we observed the GFP cells of donor-origin in a recipient.PCR,FACS analysis and FISHindicated chimerismat various intervals.Real-time PCR indicated that some donor cellsexisted in chimera for more than 6 months.Conclusions Allogenic stem cells may exist in recipients for a long time and this allogenic animal modelprovides a useful tool for studying the behavior of hematopoietic stem cells and also offers an effective modelsystem for the study of stem cells. Background It is essential to establish an animal model for the elucidation of the biological behaviors of stem cells in vivo. We constructed a chimeric animal model by in uterotransplantation for investigation of stem cell transplantation. Methods This chimerism was achieved by injecting the stem cells derived from the bone marrow of Selective methods such as aspolymerase chain reaction (PCR), real-time PCR, fluorescence-assisted cell sorting (FACS) and fluorescence in situ hybridization (FISH) were used for the observation of donor cells. Results under a fluorescence microscope, we observed the GFP cells of donor-origin in a recipient. PCR, FACS analysis and FISHindicated chimerismat various intervals. Real-time PCR indicated that some donor cell sexisted in chimera for more than 6 months .Conclusions Allogenic stem cells may exist in recipients for a long time and this allogenic animal modelprovides a useful tool for studying the behavior of hematopoietic stem cells and also offers an effective models system for the study of stem cells.