In the last decade the introduction of new drugs and protocols of treatment, together with very precise diagnoses based on the flow cytometric assessment of immunophenotype leukemic blasts, have significantly improved the survival of patients . The leukemia treatment is considered successful when bone marrow is free from leukemic cells. Even if only one neoplastic cell survives in the patient’s bone marrow, the disease can relapse. For this reason it is necessary to be sure that counted blasts in bone marrow are neoplastic cells. The aim of the study is to assess the advantages of the measurement of surface antigens expression that allows drawing the distinction between leukemia blasts and normal cells. We concluded that expression of CD45, CD10 and CD184 on leukemic blasts is different than on normal bone marrow cells and that the measurement of relative fluorescence intensity (RFI) for 2 or more antigens would simplify the search for leukemia blasts in bone marrow side population.