Abstract: BACKGROUND ＆ ATM: To establish a rapid automatic scoring method for micronucleated polychromatic erythrocytes in mice bone marrow by flow cytometer. MATERIAL AND METHODS: Treating male KM mice with cyclophosphamide(CP) and counting micronucleated cells in bone marrow and peripheral blood either by a single-laser flow cytometer(FCM)acridine orange(AO)or Giemsa, comparing the results from different methods. RESULTS: Contour configuration histograms of FL1(indicating DNA fluorescence)vs. FSC(Forward angle scatter，indicating cell size) were used to show clearly total nucleated cells(TNC)， polychromatic erythrocytes(PCE), normochromatic erythrocytes(NCE), micronucleated polychromatic erythrocytes(MNPCE) and micronucleated normochromatic erythrocytes(MNNCE)populations. CP-treated fMNPCE and fMNNCE displayed good dose-response relationship. Good correlation was demonstrated between the FCM and manual MNPCE data (r=0.973，P<0.01；r=0.978，P<0.01). C0ONCLUSION: The AO-FCM method developed in our department is applicable to detect micronucleated erythrocytes in mice bore marrow.

Key words: acridine orange, micronucleus test, flow cytometer, mice