Abstract: Objective To establish an assay method for detecting the migration of transferred apoptotic cells into the recipient using flow cytometry.Methods Spleen lymphocytes were isolated and labeled with an intracellular amine dye,carboxyfluorescein diacetate succinimidyl ester(CFSE),to allow discrimination.The labeled cells were induced with dexamethasone to undergo apoptosis and transferred into recipient mice via tail venous transfusion.Flow cytometry and histological examination of different tissues were performed at different time points.The stability of CFSE labeling for apoptotic cells was also tested.Results The CFSE-labeled apoptotic cells were highly fluorescent with a positive labeling rate of(98.0±1.9)%.The stability of CFSE-labeling was testified,and the CFSE-labeled apoptotic cells entering different tissues at different time points were detected by flow cytometry and verified by histological examination.Conclusion Flow cytometry using CFSE labeling is reliable,sensitive,precise and convenient for apoptotic cell tracing in vivo and in vitro.