BACK GROUND: THE QUANTIFICATION OF FETAL CELLS IN THE MATERNAL CIRCULATION IS AN IMPORTANT GOAL TO DETERMINE THE AMOUNT OF ANTI-D FOR PREVENTION OF ACTIVE IMMUNIZATION OF A D-NEGATIVE MOTHER GIVING BIRTH TO A D-POSITIVE BABY. AIM: THE AIM OF THIS STUDY WAS TO EVALUATE TWO FLOWCYTOMETRIC Staining FOR DETERMINATION OF FETAL ERYTHROCYTES IN MATERNAL BLOOD AND RECOGNIZE THE BEST METHOD.MATERIAL AND METHODS: 34 SAMPLES OF ADULT D-NEGATIVE BLOOD WERE SPIKED WITH SIX SERIAL DILUTION OF D-POSITIVE CORD BLOOD (10, 5, 1, 0.5, 0.25, AND 0.125%) WHICH WAS REPRESENTATIVE OF 99.9% OF THE CLINICAL FMH AND THEN WERE STAINED FOR FLOW CYTOMETRIC ANALYSIS. THE FETAL CELL COUNT KIT (IQ PRODUCT, THE NETHERLANDS) WAS USED FOR HBF DUAL Staining AND MONOCLONAL ANTI-D (IQ PRODUCT, THE NETHERLANDS) FOR RHD SINGLE Staining.