Objective    To investigate whether flow cytometry used in measuring the frequencies of micronucleated polychromatic erythrocytes (fMNPCE) can be applied as an automatic method for the early detection of low-dose irradiation caused genetic damage.     Methods    BALB/c mice were irradiated with X ray at three single low-dose (0.05

0.10

0.40 Gy respectively) for consecutive 4 days

and the frequencies of micronucleated polychromatic erythrocytes (fMNPCE) 20 h after each irradiation in bone marrow cells were detected with either flow cytometry or traditional microscopy as control method.     Results    Both flow cytometry and microscopy exhibited significantly increased fMNPCE (P0.05) after irradiation of 0.05

0.10

0.40 Gy on the first day and in the following 3 days. The fMNPCE detected by flow cytometry and microscopy showed a significant time- and dose-dependent manner and a positive correlation (r=0.984

P0.01).     Conclusion    Flow cytometry for measuring fMNPCE can be used as an automatic bio-dosimetry under low-dose irradiation.